BMC/Intel-BMC/linux.git/fs, branch dev-4.17

fix __legitimize_mnt()/mntput() race

2018-08-15T16:10:58+00:00

commit 119e1ef80ecfe0d1deb6378d4ab41f5b71519de1 upstream. __legitimize_mnt() has two problems - one is that in case of success the check of mount_lock is not ordered wrt preceding increment of refcount, making it possible to have successful __legitimize_mnt() on one CPU just before the otherwise final mntpu() on another, with __legitimize_mnt() not seeing mntput() taking the lock and mntput() not seeing the increment done by __legitimize_mnt(). Solved by a pair of barriers. Another is that failure of __legitimize_mnt() on the second read_seqretry() leaves us with reference that'll need to be dropped by caller; however, if that races with final mntput() we can end up with caller dropping rcu_read_lock() and doing mntput() to release that reference - with the first mntput() having freed the damn thing just as rcu_read_lock() had been dropped. Solution: in "do mntput() yourself" failure case grab mount_lock, check if MNT_DOOMED has been set by racing final mntput() that has missed our increment and if it has - undo the increment and treat that as "failure, caller doesn't need to drop anything" case. It's not easy to hit - the final mntput() has to come right after the first read_seqretry() in __legitimize_mnt() *and* manage to miss the increment done by __legitimize_mnt() before the second read_seqretry() in there. The things that are almost impossible to hit on bare hardware are not impossible on SMP KVM, though... Reported-by: Oleg Nesterov Fixes: 48a066e72d97 ("RCU'd vsfmounts") Cc: stable@vger.kernel.org Signed-off-by: Al Viro Signed-off-by: Greg Kroah-Hartman

fix mntput/mntput race

2018-08-15T16:10:58+00:00

commit 9ea0a46ca2c318fcc449c1e6b62a7230a17888f1 upstream. mntput_no_expire() does the calculation of total refcount under mount_lock; unfortunately, the decrement (as well as all increments) are done outside of it, leading to false positives in the "are we dropping the last reference" test. Consider the following situation: * mnt is a lazy-umounted mount, kept alive by two opened files. One of those files gets closed. Total refcount of mnt is 2. On CPU 42 mntput(mnt) (called from __fput()) drops one reference, decrementing component * After it has looked at component #0, the process on CPU 0 does mntget(), incrementing component #0, gets preempted and gets to run again - on CPU 69. There it does mntput(), which drops the reference (component #69) and proceeds to spin on mount_lock. * On CPU 42 our first mntput() finishes counting. It observes the decrement of component #69, but not the increment of component #0. As the result, the total it gets is not 1 as it should've been - it's 0. At which point we decide that vfsmount needs to be killed and proceed to free it and shut the filesystem down. However, there's still another opened file on that filesystem, with reference to (now freed) vfsmount, etc. and we are screwed. It's not a wide race, but it can be reproduced with artificial slowdown of the mnt_get_count() loop, and it should be easier to hit on SMP KVM setups. Fix consists of moving the refcount decrement under mount_lock; the tricky part is that we want (and can) keep the fast case (i.e. mount that still has non-NULL ->mnt_ns) entirely out of mount_lock. All places that zero mnt->mnt_ns are dropping some reference to mnt and they call synchronize_rcu() before that mntput(). IOW, if mntput() observes (under rcu_read_lock()) a non-NULL ->mnt_ns, it is guaranteed that there is another reference yet to be dropped. Reported-by: Jann Horn Tested-by: Jann Horn Fixes: 48a066e72d97 ("RCU'd vsfmounts") Cc: stable@vger.kernel.org Signed-off-by: Al Viro Signed-off-by: Greg Kroah-Hartman

make sure that __dentry_kill() always invalidates d_seq, unhashed or not

2018-08-15T16:10:58+00:00

commit 4c0d7cd5c8416b1ef41534d19163cb07ffaa03ab upstream. RCU pathwalk relies upon the assumption that anything that changes ->d_inode of a dentry will invalidate its ->d_seq. That's almost true - the one exception is that the final dput() of already unhashed dentry does *not* touch ->d_seq at all. Unhashing does, though, so for anything we'd found by RCU dcache lookup we are fine. Unfortunately, we can *start* with an unhashed dentry or jump into it. We could try and be careful in the (few) places where that could happen. Or we could just make the final dput() invalidate the damn thing, unhashed or not. The latter is much simpler and easier to backport, so let's do it that way. Reported-by: "Dae R. Jeong" Cc: stable@vger.kernel.org Signed-off-by: Al Viro Signed-off-by: Greg Kroah-Hartman

root dentries need RCU-delayed freeing

2018-08-15T16:10:58+00:00

commit 90bad5e05bcdb0308cfa3d3a60f5c0b9c8e2efb3 upstream. Since mountpoint crossing can happen without leaving lazy mode, root dentries do need the same protection against having their memory freed without RCU delay as everything else in the tree. It's partially hidden by RCU delay between detaching from the mount tree and dropping the vfsmount reference, but the starting point of pathwalk can be on an already detached mount, in which case umount-caused RCU delay has already passed by the time the lazy pathwalk grabs rcu_read_lock(). If the starting point happens to be at the root of that vfsmount *and* that vfsmount covers the entire filesystem, we get trouble. Fixes: 48a066e72d97 ("RCU'd vsfmounts") Cc: stable@vger.kernel.org Signed-off-by: Al Viro Signed-off-by: Greg Kroah-Hartman

jfs: Fix inconsistency between memory allocation and ea_buf->max_size

2018-08-09T10:15:13+00:00

commit 92d34134193e5b129dc24f8d79cb9196626e8d7a upstream. The code is assuming the buffer is max_size length, but we weren't allocating enough space for it. Signed-off-by: Shankara Pailoor Signed-off-by: Dave Kleikamp Cc: Guenter Roeck Signed-off-by: Greg Kroah-Hartman

xfs: validate cached inodes are free when allocated

2018-08-09T10:15:12+00:00

commit afca6c5b2595fc44383919fba740c194b0b76aff upstream. A recent fuzzed filesystem image cached random dcache corruption when the reproducer was run. This often showed up as panics in lookup_slow() on a null inode->i_ops pointer when doing pathwalks. BUG: unable to handle kernel NULL pointer dereference at 0000000000000000 .... Call Trace: lookup_slow+0x44/0x60 walk_component+0x3dd/0x9f0 link_path_walk+0x4a7/0x830 path_lookupat+0xc1/0x470 filename_lookup+0x129/0x270 user_path_at_empty+0x36/0x40 path_listxattr+0x98/0x110 SyS_listxattr+0x13/0x20 do_syscall_64+0xf5/0x280 entry_SYSCALL_64_after_hwframe+0x42/0xb7 but had many different failure modes including deadlocks trying to lock the inode that was just allocated or KASAN reports of use-after-free violations. The cause of the problem was a corrupt INOBT on a v4 fs where the root inode was marked as free in the inobt record. Hence when we allocated an inode, it chose the root inode to allocate, found it in the cache and re-initialised it. We recently fixed a similar inode allocation issue caused by inobt record corruption problem in xfs_iget_cache_miss() in commit ee457001ed6c ("xfs: catch inode allocation state mismatch corruption"). This change adds similar checks to the cache-hit path to catch it, and turns the reproducer into a corruption shutdown situation. Reported-by: Wen Xu Signed-Off-By: Dave Chinner Reviewed-by: Christoph Hellwig Reviewed-by: Carlos Maiolino Reviewed-by: Darrick J. Wong [darrick: fix typos in comment] Signed-off-by: Darrick J. Wong Cc: Eduardo Valentin Signed-off-by: Greg Kroah-Hartman

xfs: don't call xfs_da_shrink_inode with NULL bp

2018-08-09T10:15:12+00:00

commit bb3d48dcf86a97dc25fe9fc2c11938e19cb4399a upstream. xfs_attr3_leaf_create may have errored out before instantiating a buffer, for example if the blkno is out of range. In that case there is no work to do to remove it, and in fact xfs_da_shrink_inode will lead to an oops if we try. This also seems to fix a flaw where the original error from xfs_attr3_leaf_create gets overwritten in the cleanup case, and it removes a pointless assignment to bp which isn't used after this. Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=199969 Reported-by: Xu, Wen Tested-by: Xu, Wen Signed-off-by: Eric Sandeen Reviewed-by: Darrick J. Wong Signed-off-by: Darrick J. Wong Cc: Eduardo Valentin Signed-off-by: Greg Kroah-Hartman

Btrfs: fix file data corruption after cloning a range and fsync

2018-08-09T10:15:12+00:00

commit bd3599a0e142cd73edd3b6801068ac3f48ac771a upstream. When we clone a range into a file we can end up dropping existing extent maps (or trimming them) and replacing them with new ones if the range to be cloned overlaps with a range in the destination inode. When that happens we add the new extent maps to the list of modified extents in the inode's extent map tree, so that a "fast" fsync (the flag BTRFS_INODE_NEEDS_FULL_SYNC not set in the inode) will see the extent maps and log corresponding extent items. However, at the end of range cloning operation we do truncate all the pages in the affected range (in order to ensure future reads will not get stale data). Sometimes this truncation will release the corresponding extent maps besides the pages from the page cache. If this happens, then a "fast" fsync operation will miss logging some extent items, because it relies exclusively on the extent maps being present in the inode's extent tree, leading to data loss/corruption if the fsync ends up using the same transaction used by the clone operation (that transaction was not committed in the meanwhile). An extent map is released through the callback btrfs_invalidatepage(), which gets called by truncate_inode_pages_range(), and it calls __btrfs_releasepage(). The later ends up calling try_release_extent_mapping() which will release the extent map if some conditions are met, like the file size being greater than 16Mb, gfp flags allow blocking and the range not being locked (which is the case during the clone operation) nor being the extent map flagged as pinned (also the case for cloning). The following example, turned into a test for fstests, reproduces the issue: $ mkfs.btrfs -f /dev/sdb $ mount /dev/sdb /mnt $ xfs_io -f -c "pwrite -S 0x18 9000K 6908K" /mnt/foo $ xfs_io -f -c "pwrite -S 0x20 2572K 156K" /mnt/bar $ xfs_io -c "fsync" /mnt/bar # reflink destination offset corresponds to the size of file bar, # 2728Kb minus 4Kb. $ xfs_io -c ""reflink ${SCRATCH_MNT}/foo 0 2724K 15908K" /mnt/bar $ xfs_io -c "fsync" /mnt/bar $ md5sum /mnt/bar 95a95813a8c2abc9aa75a6c2914a077e /mnt/bar $ mount /dev/sdb /mnt $ md5sum /mnt/bar 207fd8d0b161be8a84b945f0df8d5f8d /mnt/bar # digest should be 95a95813a8c2abc9aa75a6c2914a077e like before the # power failure In the above example, the destination offset of the clone operation corresponds to the size of the "bar" file minus 4Kb. So during the clone operation, the extent map covering the range from 2572Kb to 2728Kb gets trimmed so that it ends at offset 2724Kb, and a new extent map covering the range from 2724Kb to 11724Kb is created. So at the end of the clone operation when we ask to truncate the pages in the range from 2724Kb to 2724Kb + 15908Kb, the page invalidation callback ends up removing the new extent map (through try_release_extent_mapping()) when the page at offset 2724Kb is passed to that callback. Fix this by setting the bit BTRFS_INODE_NEEDS_FULL_SYNC whenever an extent map is removed at try_release_extent_mapping(), forcing the next fsync to search for modified extents in the fs/subvolume tree instead of relying on the presence of extent maps in memory. This way we can continue doing a "fast" fsync if the destination range of a clone operation does not overlap with an existing range or if any of the criteria necessary to remove an extent map at try_release_extent_mapping() is not met (file size not bigger then 16Mb or gfp flags do not allow blocking). CC: stable@vger.kernel.org # 3.16+ Signed-off-by: Filipe Manana Signed-off-by: David Sterba Signed-off-by: Sudip Mukherjee Signed-off-by: Greg Kroah-Hartman

jfs: Fix usercopy whitelist for inline inode data

2018-08-09T10:15:11+00:00

commit 961b33c244e5ba1543ae26270a1ba29f29c2db83 upstream. Bart Massey reported what turned out to be a usercopy whitelist false positive in JFS when symlink contents exceeded 128 bytes. The inline inode data (i_inline) is actually designed to overflow into the "extended area" following it (i_inline_ea) when needed. So the whitelist needed to be expanded to include both i_inline and i_inline_ea (the whole size of which is calculated internally using IDATASIZE, 256, instead of sizeof(i_inline), 128). $ cd /mnt/jfs $ touch $(perl -e 'print "B" x 250') $ ln -s B* b $ ls -l >/dev/null [ 249.436410] Bad or missing usercopy whitelist? Kernel memory exposure attempt detected from SLUB object 'jfs_ip' (offset 616, size 250)! Reported-by: Bart Massey Fixes: 8d2704d382a9 ("jfs: Define usercopy region in jfs_ip slab cache") Cc: Dave Kleikamp Cc: jfs-discussion@lists.sourceforge.net Cc: stable@vger.kernel.org Signed-off-by: Kees Cook Signed-off-by: Greg Kroah-Hartman

userfaultfd: remove uffd flags from vma->vm_flags if UFFD_EVENT_FORK fails

2018-08-06T14:18:21+00:00

commit 31e810aa1033a7db50a2746cd34a2432237f6420 upstream. The fix in commit 0cbb4b4f4c44 ("userfaultfd: clear the vma->vm_userfaultfd_ctx if UFFD_EVENT_FORK fails") cleared the vma->vm_userfaultfd_ctx but kept userfaultfd flags in vma->vm_flags that were copied from the parent process VMA. As the result, there is an inconsistency between the values of vma->vm_userfaultfd_ctx.ctx and vma->vm_flags which triggers BUG_ON in userfaultfd_release(). Clearing the uffd flags from vma->vm_flags in case of UFFD_EVENT_FORK failure resolves the issue. Link: http://lkml.kernel.org/r/1532931975-25473-1-git-send-email-rppt@linux.vnet.ibm.com Fixes: 0cbb4b4f4c44 ("userfaultfd: clear the vma->vm_userfaultfd_ctx if UFFD_EVENT_FORK fails") Signed-off-by: Mike Rapoport Reported-by: syzbot+121be635a7a35ddb7dcb@syzkaller.appspotmail.com Cc: Andrea Arcangeli Cc: Eric Biggers Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman