kernel/linux.git/fs/afs/super.c, branch linux-6.0.y

netfs: Fix gcc-12 warning by embedding vfs inode in netfs_i_context

2022-06-09T20:55:00+00:00

While randstruct was satisfied with using an open-coded "void *" offset cast for the netfs_i_context <-> inode casting, __builtin_object_size() as used by FORTIFY_SOURCE was not as easily fooled. This was causing the following complaint[1] from gcc v12: In file included from include/linux/string.h:253, from include/linux/ceph/ceph_debug.h:7, from fs/ceph/inode.c:2: In function 'fortify_memset_chk', inlined from 'netfs_i_context_init' at include/linux/netfs.h:326:2, inlined from 'ceph_alloc_inode' at fs/ceph/inode.c:463:2: include/linux/fortify-string.h:242:25: warning: call to '__write_overflow_field' declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Wattribute-warning] 242 | __write_overflow_field(p_size_field, size); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Fix this by embedding a struct inode into struct netfs_i_context (which should perhaps be renamed to struct netfs_inode). The struct inode vfs_inode fields are then removed from the 9p, afs, ceph and cifs inode structs and vfs_inode is then simply changed to "netfs.inode" in those filesystems. Further, rename netfs_i_context to netfs_inode, get rid of the netfs_inode() function that converted a netfs_i_context pointer to an inode pointer (that can now be done with &ctx->inode) and rename the netfs_i_context() function to netfs_inode() (which is now a wrapper around container_of()). Most of the changes were done with: perl -p -i -e 's/vfs_inode/netfs.inode/'g \ `git grep -l 'vfs_inode' -- fs/{9p,afs,ceph,cifs}/*.[ch]` Kees suggested doing it with a pair structure[2] and a special declarator to insert that into the network filesystem's inode wrapper[3], but I think it's cleaner to embed it - and then it doesn't matter if struct randomisation reorders things. Dave Chinner suggested using a filesystem-specific VFS_I() function in each filesystem to convert that filesystem's own inode wrapper struct into the VFS inode struct[4]. Version #2: - Fix a couple of missed name changes due to a disabled cifs option. - Rename nfs_i_context to nfs_inode - Use "netfs" instead of "nic" as the member name in per-fs inode wrapper structs. [ This also undoes commit 507160f46c55 ("netfs: gcc-12: temporarily disable '-Wattribute-warning' for now") that is no longer needed ] Fixes: bc899ee1c898 ("netfs: Add a netfs inode context") Reported-by: Jeff Layton Signed-off-by: David Howells Reviewed-by: Jeff Layton Reviewed-by: Kees Cook Reviewed-by: Xiubo Li cc: Jonathan Corbet cc: Eric Van Hensbergen cc: Latchesar Ionkov cc: Dominique Martinet cc: Christian Schoenebeck cc: Marc Dionne cc: Ilya Dryomov cc: Steve French cc: William Kucharski cc: "Matthew Wilcox (Oracle)" cc: Dave Chinner cc: linux-doc@vger.kernel.org cc: v9fs-developer@lists.sourceforge.net cc: linux-afs@lists.infradead.org cc: ceph-devel@vger.kernel.org cc: linux-cifs@vger.kernel.org cc: samba-technical@lists.samba.org cc: linux-fsdevel@vger.kernel.org cc: linux-hardening@vger.kernel.org Link: https://lore.kernel.org/r/d2ad3a3d7bdd794c6efb562d2f2b655fb67756b9.camel@kernel.org/ [1] Link: https://lore.kernel.org/r/20220517210230.864239-1-keescook@chromium.org/ [2] Link: https://lore.kernel.org/r/20220518202212.2322058-1-keescook@chromium.org/ [3] Link: https://lore.kernel.org/r/20220524101205.GI2306852@dread.disaster.area/ [4] Link: https://lore.kernel.org/r/165296786831.3591209.12111293034669289733.stgit@warthog.procyon.org.uk/ # v1 Link: https://lore.kernel.org/r/165305805651.4094995.7763502506786714216.stgit@warthog.procyon.org.uk # v2 Signed-off-by: Linus Torvalds

Merge tag 'netfs-prep-20220318' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs

2022-03-31T22:49:36+00:00

Pull netfs updates from David Howells: "Netfs prep for write helpers. Having had a go at implementing write helpers and content encryption support in netfslib, it seems that the netfs_read_{,sub}request structs and the equivalent write request structs were almost the same and so should be merged, thereby requiring only one set of alloc/get/put functions and a common set of tracepoints. Merging the structs also has the advantage that if a bounce buffer is added to the request struct, a read operation can be performed to fill the bounce buffer, the contents of the buffer can be modified and then a write operation can be performed on it to send the data wherever it needs to go using the same request structure all the way through. The I/O handlers would then transparently perform any required crypto. This should make it easier to perform RMW cycles if needed. The potentially common functions and structs, however, by their names all proclaim themselves to be associated with the read side of things. The bulk of these changes alter this in the following ways: - Rename struct netfs_read_{,sub}request to netfs_io_{,sub}request. - Rename some enums, members and flags to make them more appropriate. - Adjust some comments to match. - Drop "read"/"rreq" from the names of common functions. For instance, netfs_get_read_request() becomes netfs_get_request(). - The ->init_rreq() and ->issue_op() methods become ->init_request() and ->issue_read(). I've kept the latter as a read-specific function and in another branch added an ->issue_write() method. The driver source is then reorganised into a number of files: fs/netfs/buffered_read.c Create read reqs to the pagecache fs/netfs/io.c Dispatchers for read and write reqs fs/netfs/main.c Some general miscellaneous bits fs/netfs/objects.c Alloc, get and put functions fs/netfs/stats.c Optional procfs statistics. and future development can be fitted into this scheme, e.g.: fs/netfs/buffered_write.c Modify the pagecache fs/netfs/buffered_flush.c Writeback from the pagecache fs/netfs/direct_read.c DIO read support fs/netfs/direct_write.c DIO write support fs/netfs/unbuffered_write.c Write modifications directly back Beyond the above changes, there are also some changes that affect how things work: - Make fscache_end_operation() generally available. - In the netfs tracing header, generate enums from the symbol -> string mapping tables rather than manually coding them. - Add a struct for filesystems that uses netfslib to put into their inode wrapper structs to hold extra state that netfslib is interested in, such as the fscache cookie. This allows netfslib functions to be set in filesystem operation tables and jumped to directly without having to have a filesystem wrapper. - Add a member to the struct added above to track the remote inode length as that may differ if local modifications are buffered. We may need to supply an appropriate EOF pointer when storing data (in AFS for example). - Pass extra information to netfs_alloc_request() so that the ->init_request() hook can access it and retain information to indicate the origin of the operation. - Make the ->init_request() hook return an error, thereby allowing a filesystem that isn't allowed to cache an inode (ceph or cifs, for example) to skip readahead. - Switch to using refcount_t for subrequests and add tracepoints to log refcount changes for the request and subrequest structs. - Add a function to consolidate dispatching a read request. Similar code is used in three places and another couple are likely to be added in the future" Link: https://lore.kernel.org/all/2639515.1648483225@warthog.procyon.org.uk/ * tag 'netfs-prep-20220318' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs: afs: Maintain netfs_i_context::remote_i_size netfs: Keep track of the actual remote file size netfs: Split some core bits out into their own file netfs: Split fs/netfs/read_helper.c netfs: Rename read_helper.c to io.c netfs: Prepare to split read_helper.c netfs: Add a function to consolidate beginning a read netfs: Add a netfs inode context ceph: Make ceph_init_request() check caps on readahead netfs: Change ->init_request() to return an error code netfs: Refactor arguments for netfs_alloc_read_request netfs: Adjust the netfs_failure tracepoint to indicate non-subreq lines netfs: Trace refcounting on the netfs_io_subrequest struct netfs: Trace refcounting on the netfs_io_request struct netfs: Adjust the netfs_rreq tracepoint slightly netfs: Split netfs_io_* object handling out netfs: Finish off rename of netfs_read_request to netfs_io_request netfs: Rename netfs_read_*request to netfs_io_*request netfs: Generate enums from trace symbol mapping lists fscache: export fscache_end_operation()

fs: allocate inode by using alloc_inode_sb()

2022-03-22T22:57:03+00:00

The inode allocation is supposed to use alloc_inode_sb(), so convert kmem_cache_alloc() of all filesystems to alloc_inode_sb(). Link: https://lkml.kernel.org/r/20220228122126.37293-5-songmuchun@bytedance.com Signed-off-by: Muchun Song Acked-by: Theodore Ts'o [ext4] Acked-by: Roman Gushchin Cc: Alex Shi Cc: Anna Schumaker Cc: Chao Yu Cc: Dave Chinner Cc: Fam Zheng Cc: Jaegeuk Kim Cc: Johannes Weiner Cc: Kari Argillander Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Qi Zheng Cc: Shakeel Butt Cc: Trond Myklebust Cc: Vladimir Davydov Cc: Vlastimil Babka Cc: Wei Yang Cc: Xiongchun Duan Cc: Yang Shi Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

netfs: Add a netfs inode context

2022-03-18T09:29:05+00:00

Add a netfs_i_context struct that should be included in the network filesystem's own inode struct wrapper, directly after the VFS's inode struct, e.g.: struct my_inode { struct { /* These must be contiguous */ struct inode vfs_inode; struct netfs_i_context netfs_ctx; }; }; The netfs_i_context struct so far contains a single field for the network filesystem to use - the cache cookie: struct netfs_i_context { ... struct fscache_cookie *cache; }; Three functions are provided to help with this: (1) void netfs_i_context_init(struct inode *inode, const struct netfs_request_ops *ops); Initialise the netfs context and set the operations. (2) struct netfs_i_context *netfs_i_context(struct inode *inode); Find the netfs context from the VFS inode. (3) struct inode *netfs_inode(struct netfs_i_context *ctx); Find the VFS inode from the netfs context. Changes ======= ver #4) - Fix netfs_is_cache_enabled() to check cookie->cache_priv to see if a cache is present[3]. - Fix netfs_skip_folio_read() to zero out all of the page, not just some of it[3]. ver #3) - Split out the bit to move ceph cap-getting on readahead into ceph_init_request()[1]. - Stick in a comment to the netfs inode structs indicating the contiguity requirements[2]. ver #2) - Adjust documentation to match. - Use "#if IS_ENABLED()" in netfs_i_cookie(), not "#ifdef". - Move the cap check from ceph_readahead() to ceph_init_request() to be called from netfslib. - Remove ceph_readahead() and use netfs_readahead() directly instead. Signed-off-by: David Howells Acked-by: Jeff Layton cc: linux-cachefs@redhat.com Link: https://lore.kernel.org/r/8af0d47f17d89c06bbf602496dd845f2b0bf25b3.camel@kernel.org/ [1] Link: https://lore.kernel.org/r/beaf4f6a6c2575ed489adb14b257253c868f9a5c.camel@kernel.org/ [2] Link: https://lore.kernel.org/r/3536452.1647421585@warthog.procyon.org.uk/ [3] Link: https://lore.kernel.org/r/164622984545.3564931.15691742939278418580.stgit@warthog.procyon.org.uk/ # v1 Link: https://lore.kernel.org/r/164678213320.1200972.16807551936267647470.stgit@warthog.procyon.org.uk/ # v2 Link: https://lore.kernel.org/r/164692909854.2099075.9535537286264248057.stgit@warthog.procyon.org.uk/ # v3 Link: https://lore.kernel.org/r/306388.1647595110@warthog.procyon.org.uk/ # v4

Merge tag 'fscache-rewrite-20220111' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs

2022-01-12T21:45:12+00:00

Pull fscache rewrite from David Howells: "This is a set of patches that rewrites the fscache driver and the cachefiles driver, significantly simplifying the code compared to what's upstream, removing the complex operation scheduling and object state machine in favour of something much smaller and simpler. The series is structured such that the first few patches disable fscache use by the network filesystems using it, remove the cachefiles driver entirely and as much of the fscache driver as can be got away with without causing build failures in the network filesystems. The patches after that recreate fscache and then cachefiles, attempting to add the pieces in a logical order. Finally, the filesystems are reenabled and then the very last patch changes the documentation. [!] Note: I have dropped the cifs patch for the moment, leaving local caching in cifs disabled. I've been having trouble getting that working. I think I have it done, but it needs more testing (there seem to be some test failures occurring with v5.16 also from xfstests), so I propose deferring that patch to the end of the merge window. WHY REWRITE? ============ Fscache's operation scheduling API was intended to handle sequencing of cache operations, which were all required (where possible) to run asynchronously in parallel with the operations being done by the network filesystem, whilst allowing the cache to be brought online and offline and to interrupt service for invalidation. With the advent of the tmpfile capacity in the VFS, however, an opportunity arises to do invalidation much more simply, without having to wait for I/O that's actually in progress: Cachefiles can simply create a tmpfile, cut over the file pointer for the backing object attached to a cookie and abandon the in-progress I/O, dismissing it upon completion. Future work here would involve using Omar Sandoval's vfs_link() with AT_LINK_REPLACE[1] to allow an extant file to be displaced by a new hard link from a tmpfile as currently I have to unlink the old file first. These patches can also simplify the object state handling as I/O operations to the cache don't all have to be brought to a stop in order to invalidate a file. To that end, and with an eye on to writing a new backing cache model in the future, I've taken the opportunity to simplify the indexing structure. I've separated the index cookie concept from the file cookie concept by C type now. The former is now called a "volume cookie" (struct fscache_volume) and there is a container of file cookies. There are then just the two levels. All the index cookie levels are collapsed into a single volume cookie, and this has a single printable string as a key. For instance, an AFS volume would have a key of something like "afs,example.com,1000555", combining the filesystem name, cell name and volume ID. This is freeform, but must not have '/' chars in it. I've also eliminated all pointers back from fscache into the network filesystem. This required the duplication of a little bit of data in the cookie (cookie key, coherency data and file size), but it's not actually that much. This gets rid of problems with making sure we keep netfs data structures around so that the cache can access them. These patches mean that most of the code that was in the drivers before is simply gone and those drivers are now almost entirely new code. That being the case, there doesn't seem any particular reason to try and maintain bisectability across it. Further, there has to be a point in the middle where things are cut over as there's a single point everything has to go through (ie. /dev/cachefiles) and it can't be in use by two drivers at once. ISSUES YET OUTSTANDING ====================== There are some issues still outstanding, unaddressed by this patchset, that will need fixing in future patchsets, but that don't stop this series from being usable: (1) The cachefiles driver needs to stop using the backing filesystem's metadata to store information about what parts of the cache are populated. This is not reliable with modern extent-based filesystems. Fixing this is deferred to a separate patchset as it involves negotiation with the network filesystem and the VM as to how much data to download to fulfil a read - which brings me on to (2)... (2) NFS (and CIFS with the dropped patch) do not take account of how the cache would like I/O to be structured to meet its granularity requirements. Previously, the cache used page granularity, which was fine as the network filesystems also dealt in page granularity, and the backing filesystem (ext4, xfs or whatever) did whatever it did out of sight. However, we now have folios to deal with and the cache will now have to store its own metadata to track its contents. The change I'm looking at making for cachefiles is to store content bitmaps in one or more xattrs and making a bit in the map correspond to something like a 256KiB block. However, the size of an xattr and the fact that they have to be read/updated in one go means that I'm looking at covering 1GiB of data per 512-byte map and storing each map in an xattr. Cachefiles has the potential to grow into a fully fledged filesystem of its very own if I'm not careful. However, I'm also looking at changing things even more radically and going to a different model of how the cache is arranged and managed - one that's more akin to the way, say, openafs does things - which brings me on to (3)... (3) The way cachefilesd does culling is very inefficient for large caches and it would be better to move it into the kernel if I can as cachefilesd has to keep asking the kernel if it can cull a file. Changing the way the backend works would allow this to be addressed. BITS THAT MAY BE CONTROVERSIAL ============================== There are some bits I've added that may be controversial: (1) I've provided a flag, S_KERNEL_FILE, that cachefiles uses to check if a files is already being used by some other kernel service (e.g. a duplicate cachefiles cache in the same directory) and reject it if it is. This isn't entirely necessary, but it helps prevent accidental data corruption. I don't want to use S_SWAPFILE as that has other effects, but quite possibly swapon() should set S_KERNEL_FILE too. Note that it doesn't prevent userspace from interfering, though perhaps it should. (I have made it prevent a marked directory from being rmdir-able). (2) Cachefiles wants to keep the backing file for a cookie open whilst we might need to write to it from network filesystem writeback. The problem is that the network filesystem unuses its cookie when its file is closed, and so we have nothing pinning the cachefiles file open and it will get closed automatically after a short time to avoid EMFILE/ENFILE problems. Reopening the cache file, however, is a problem if this is being done due to writeback triggered by exit(). Some filesystems will oops if we try to open a file in that context because they want to access current->fs or suchlike. To get around this, I added the following: (A) An inode flag, I_PINNING_FSCACHE_WB, to be set on a network filesystem inode to indicate that we have a usage count on the cookie caching that inode. (B) A flag in struct writeback_control, unpinned_fscache_wb, that is set when __writeback_single_inode() clears the last dirty page from i_pages - at which point it clears I_PINNING_FSCACHE_WB and sets this flag. This has to be done here so that clearing I_PINNING_FSCACHE_WB can be done atomically with the check of PAGECACHE_TAG_DIRTY that clears I_DIRTY_PAGES. (C) A function, fscache_set_page_dirty(), which if it is not set, sets I_PINNING_FSCACHE_WB and calls fscache_use_cookie() to pin the cache resources. (D) A function, fscache_unpin_writeback(), to be called by ->write_inode() to unuse the cookie. (E) A function, fscache_clear_inode_writeback(), to be called when the inode is evicted, before clear_inode() is called. This cleans up any lingering I_PINNING_FSCACHE_WB. The network filesystem can then use these tools to make sure that fscache_write_to_cache() can write locally modified data to the cache as well as to the server. For the future, I'm working on write helpers for netfs lib that should allow this facility to be removed by keeping track of the dirty regions separately - but that's incomplete at the moment and is also going to be affected by folios, one way or another, since it deals with pages" Link: https://lore.kernel.org/all/510611.1641942444@warthog.procyon.org.uk/ Tested-by: Dominique Martinet # 9p Tested-by: kafs-testing@auristor.com # afs Tested-by: Jeff Layton # ceph Tested-by: Dave Wysochanski # nfs Tested-by: Daire Byrne # nfs * tag 'fscache-rewrite-20220111' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs: (67 commits) 9p, afs, ceph, nfs: Use current_is_kswapd() rather than gfpflags_allow_blocking() fscache: Add a tracepoint for cookie use/unuse fscache: Rewrite documentation ceph: add fscache writeback support ceph: conversion to new fscache API nfs: Implement cache I/O by accessing the cache directly nfs: Convert to new fscache volume/cookie API 9p: Copy local writes to the cache when writing to the server 9p: Use fscache indexing rewrite and reenable caching afs: Skip truncation on the server of data we haven't written yet afs: Copy local writes to the cache when writing to the server afs: Convert afs to use the new fscache API fscache, cachefiles: Display stat of culling events fscache, cachefiles: Display stats of no-space events cachefiles: Allow cachefiles to actually function fscache, cachefiles: Store the volume coherency data cachefiles: Implement the I/O routines cachefiles: Implement cookie resize for truncate cachefiles: Implement begin and end I/O operation cachefiles: Implement backing file wrangling ...

afs: Copy local writes to the cache when writing to the server

2022-01-07T13:44:52+00:00

When writing to the server from afs_writepage() or afs_writepages(), copy the data to the cache object too. To make this possible, the cookie must have its active users count incremented when the page is dirtied and kept incremented until we manage to clean up all the pages. This allows the writeback to take place after the last file struct is released. Signed-off-by: David Howells Tested-by: kafs-testing@auristor.com Acked-by: Jeff Layton cc: Marc Dionne cc: linux-afs@lists.infradead.org cc: linux-cachefs@redhat.com Link: https://lore.kernel.org/r/163819662333.215744.7531373404219224438.stgit@warthog.procyon.org.uk/ # v1 Link: https://lore.kernel.org/r/163906970998.143852.674420788614608063.stgit@warthog.procyon.org.uk/ # v2 Link: https://lore.kernel.org/r/163967176564.1823006.16666056085593949570.stgit@warthog.procyon.org.uk/ # v3 Link: https://lore.kernel.org/r/164021570208.640689.9193494979708031862.stgit@warthog.procyon.org.uk/ # v4

afs: Fix mmap

2021-12-16T17:10:13+00:00

Fix afs_add_open_map() to check that the vnode isn't already on the list when it adds it. It's possible that afs_drop_open_mmap() decremented the cb_nr_mmap counter, but hadn't yet got into the locked section to remove it. Also vnode->cb_mmap_link should be initialised, so fix that too. Fixes: 6e0e99d58a65 ("afs: Fix mmap coherency vs 3rd-party changes") Reported-by: kafs-testing+fedora34_64checkkafs-build-300@auristor.com Suggested-by: Marc Dionne Signed-off-by: David Howells Tested-by: kafs-testing+fedora34_64checkkafs-build-300@auristor.com cc: linux-afs@lists.infradead.org Link: https://lore.kernel.org/r/686465.1639435380@warthog.procyon.org.uk/ # v1 Signed-off-by: Linus Torvalds

afs: Fix mmap coherency vs 3rd-party changes

2021-09-13T08:10:39+00:00

Fix the coherency management of mmap'd data such that 3rd-party changes become visible as soon as possible after the callback notification is delivered by the fileserver. This is done by the following means: (1) When we break a callback on a vnode specified by the CB.CallBack call from the server, we queue a work item (vnode->cb_work) to go and clobber all the PTEs mapping to that inode. This causes the CPU to trip through the ->map_pages() and ->page_mkwrite() handlers if userspace attempts to access the page(s) again. (Ideally, this would be done in the service handler for CB.CallBack, but the server is waiting for our reply before considering, and we have a list of vnodes, all of which need breaking - and the process of getting the mmap_lock and stripping the PTEs on all CPUs could be quite slow.) (2) Call afs_validate() from the ->map_pages() handler to check to see if the file has changed and to get a new callback promise from the server. Also handle the fileserver telling us that it's dropping all callbacks, possibly after it's been restarted by sending us a CB.InitCallBackState* call by the following means: (3) Maintain a per-cell list of afs files that are currently mmap'd (cell->fs_open_mmaps). (4) Add a work item to each server that is invoked if there are any open mmaps when CB.InitCallBackState happens. This work item goes through the aforementioned list and invokes the vnode->cb_work work item for each one that is currently using this server. This causes the PTEs to be cleared, causing ->map_pages() or ->page_mkwrite() to be called again, thereby calling afs_validate() again. I've chosen to simply strip the PTEs at the point of notification reception rather than invalidate all the pages as well because (a) it's faster, (b) we may get a notification for other reasons than the data being altered (in which case we don't want to clobber the pagecache) and (c) we need to ask the server to find out - and I don't want to wait for the reply before holding up userspace. This was tested using the attached test program: #include #include #include #include #include #include int main(int argc, char *argv[]) { size_t size = getpagesize(); unsigned char *p; bool mod = (argc == 3); int fd; if (argc != 2 && argc != 3) { fprintf(stderr, "Format: %s [mod]\n", argv[0]); exit(2); } fd = open(argv[1], mod ? O_RDWR : O_RDONLY); if (fd < 0) { perror(argv[1]); exit(1); } p = mmap(NULL, size, mod ? PROT_READ|PROT_WRITE : PROT_READ, MAP_SHARED, fd, 0); if (p == MAP_FAILED) { perror("mmap"); exit(1); } for (;;) { if (mod) { p[0]++; msync(p, size, MS_ASYNC); fsync(fd); } printf("%02x", p[0]); fflush(stdout); sleep(1); } } It runs in two modes: in one mode, it mmaps a file, then sits in a loop reading the first byte, printing it and sleeping for a second; in the second mode it mmaps a file, then sits in a loop incrementing the first byte and flushing, then printing and sleeping. Two instances of this program can be run on different machines, one doing the reading and one doing the writing. The reader should see the changes made by the writer, but without this patch, they aren't because validity checking is being done lazily - only on entry to the filesystem. Testing the InitCallBackState change is more complicated. The server has to be taken offline, the saved callback state file removed and then the server restarted whilst the reading-mode program continues to run. The client machine then has to poke the server to trigger the InitCallBackState call. Signed-off-by: David Howells Tested-by: Markus Suvanto cc: linux-afs@lists.infradead.org Link: https://lore.kernel.org/r/163111668833.283156.382633263709075739.stgit@warthog.procyon.org.uk/

afs: Fix memory leak when mounting with multiple source parameters

2020-12-08T23:59:25+00:00

There's a memory leak in afs_parse_source() whereby multiple source= parameters overwrite fc->source in the fs_context struct without freeing the previously recorded source. Fix this by only permitting a single source parameter and rejecting with an error all subsequent ones. This was caught by syzbot with the kernel memory leak detector, showing something like the following trace: unreferenced object 0xffff888114375440 (size 32): comm "repro", pid 5168, jiffies 4294923723 (age 569.948s) backtrace: slab_post_alloc_hook+0x42/0x79 __kmalloc_track_caller+0x125/0x16a kmemdup_nul+0x24/0x3c vfs_parse_fs_string+0x5a/0xa1 generic_parse_monolithic+0x9d/0xc5 do_new_mount+0x10d/0x15a do_mount+0x5f/0x8e __do_sys_mount+0xff/0x127 do_syscall_64+0x2d/0x3a entry_SYSCALL_64_after_hwframe+0x44/0xa9 Fixes: 13fcc6837049 ("afs: Add fs_context support") Reported-by: syzbot+86dc6632faaca40133ab@syzkaller.appspotmail.com Signed-off-by: David Howells cc: Randy Dunlap Signed-off-by: Linus Torvalds

Merge tag 'afs-fixes-20201016' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs

2020-10-16T22:22:41+00:00

Pull afs updates from David Howells: "A collection of fixes to fix afs_cell struct refcounting, thereby fixing a slew of related syzbot bugs: - Fix the cell tree in the netns to use an rwsem rather than RCU. There seem to be some problems deriving from the use of RCU and a seqlock to walk the rbtree, but it's not entirely clear what since there are several different failures being seen. Changing things to use an rwsem instead makes it more robust. The extra performance derived from using RCU isn't necessary in this case since the only time we're looking up a cell is during mount or when cells are being manually added. - Fix the refcounting by splitting the usage counter into a memory refcount and an active users counter. The usage counter was doing double duty, keeping track of whether a cell is still in use and keeping track of when it needs to be destroyed - but this makes the clean up tricky. Separating these out simplifies the logic. - Fix purging a cell that has an alias. A cell alias pins the cell it's an alias of, but the alias is always later in the list. Trying to purge in a single pass causes rmmod to hang in such a case. - Fix cell removal. If a cell's manager is requeued whilst it's removing itself, the manager will run again and re-remove itself, causing problems in various places. Follow Hillf Danton's suggestion to insert a more terminal state that causes the manager to do nothing post-removal. In additional to the above, two other changes: - Add a tracepoint for the cell refcount and active users count. This helped with debugging the above and may be useful again in future. - Downgrade an assertion to a print when a still-active server is seen during purging. This was happening as a consequence of incomplete cell removal before the servers were cleaned up" * tag 'afs-fixes-20201016' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs: afs: Don't assert on unpurgeable server records afs: Add tracing for cell refcount and active user count afs: Fix cell removal afs: Fix cell purging with aliases afs: Fix cell refcounting by splitting the usage counter afs: Fix rapid cell addition/removal by not using RCU on cells tree