kernel/linux.git/mm/slab_common.c, branch v4.14.265

mm/slab: use memzero_explicit() in kzfree()

2020-06-30T19:38:08+00:00

commit 8982ae527fbef170ef298650c15d55a9ccd33973 upstream. The kzfree() function is normally used to clear some sensitive information, like encryption keys, in the buffer before freeing it back to the pool. Memset() is currently used for buffer clearing. However unlikely, there is still a non-zero probability that the compiler may choose to optimize away the memory clearing especially if LTO is being used in the future. To make sure that this optimization will never happen, memzero_explicit(), which is introduced in v3.18, is now used in kzfree() to future-proof it. Link: http://lkml.kernel.org/r/20200616154311.12314-2-longman@redhat.com Fixes: 3ef0e5ba4673 ("slab: introduce kzfree()") Signed-off-by: Waiman Long Acked-by: Michal Hocko Cc: David Howells Cc: Jarkko Sakkinen Cc: James Morris Cc: "Serge E. Hallyn" Cc: Joe Perches Cc: Matthew Wilcox Cc: David Rientjes Cc: Johannes Weiner Cc: Dan Carpenter Cc: "Jason A . Donenfeld" Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

mm: don't warn about large allocations for slab

2018-12-01T08:42:51+00:00

commit 61448479a9f2c954cde0cfe778cb6bec5d0a748d upstream. Slub does not call kmalloc_slab() for sizes > KMALLOC_MAX_CACHE_SIZE, instead it falls back to kmalloc_large(). For slab KMALLOC_MAX_CACHE_SIZE == KMALLOC_MAX_SIZE and it calls kmalloc_slab() for all allocations relying on NULL return value for over-sized allocations. This inconsistency leads to unwanted warnings from kmalloc_slab() for over-sized allocations for slab. Returning NULL for failed allocations is the expected behavior. Make slub and slab code consistent by checking size > KMALLOC_MAX_CACHE_SIZE in slab before calling kmalloc_slab(). While we are here also fix the check in kmalloc_slab(). We should check against KMALLOC_MAX_CACHE_SIZE rather than KMALLOC_MAX_SIZE. It all kinda worked because for slab the constants are the same, and slub always checks the size against KMALLOC_MAX_CACHE_SIZE before kmalloc_slab(). But if we get there with size > KMALLOC_MAX_CACHE_SIZE anyhow bad things will happen. For example, in case of a newly introduced bug in slub code. Also move the check in kmalloc_slab() from function entry to the size > 192 case. This partially compensates for the additional check in slab code and makes slub code a bit faster (at least theoretically). Also drop __GFP_NOWARN in the warning check. This warning means a bug in slab code itself, user-passed flags have nothing to do with it. Nothing of this affects slob. Link: http://lkml.kernel.org/r/20180927171502.226522-1-dvyukov@gmail.com Signed-off-by: Dmitry Vyukov Reported-by: syzbot+87829a10073277282ad1@syzkaller.appspotmail.com Reported-by: syzbot+ef4e8fc3a06e9019bb40@syzkaller.appspotmail.com Reported-by: syzbot+6e438f4036df52cbb863@syzkaller.appspotmail.com Reported-by: syzbot+8574471d8734457d98aa@syzkaller.appspotmail.com Reported-by: syzbot+af1504df0807a083dbd9@syzkaller.appspotmail.com Acked-by: Christoph Lameter Acked-by: Vlastimil Babka Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

slub: fix failure when we delete and create a slab cache

2018-07-03T09:25:04+00:00

commit d50d82faa0c964e31f7a946ba8aba7c715ca7ab0 upstream. In kernel 4.17 I removed some code from dm-bufio that did slab cache merging (commit 21bb13276768: "dm bufio: remove code that merges slab caches") - both slab and slub support merging caches with identical attributes, so dm-bufio now just calls kmem_cache_create and relies on implicit merging. This uncovered a bug in the slub subsystem - if we delete a cache and immediatelly create another cache with the same attributes, it fails because of duplicate filename in /sys/kernel/slab/. The slub subsystem offloads freeing the cache to a workqueue - and if we create the new cache before the workqueue runs, it complains because of duplicate filename in sysfs. This patch fixes the bug by moving the call of kobject_del from sysfs_slab_remove_workfn to shutdown_cache. kobject_del must be called while we hold slab_mutex - so that the sysfs entry is deleted before a cache with the same attributes could be created. Running device-mapper-test-suite with: dmtest run --suite thin-provisioning -n /commit_failure_causes_fallback/ triggered: Buffer I/O error on dev dm-0, logical block 1572848, async page read device-mapper: thin: 253:1: metadata operation 'dm_pool_alloc_data_block' failed: error = -5 device-mapper: thin: 253:1: aborting current metadata transaction sysfs: cannot create duplicate filename '/kernel/slab/:a-0000144' CPU: 2 PID: 1037 Comm: kworker/u48:1 Not tainted 4.17.0.snitm+ #25 Hardware name: Supermicro SYS-1029P-WTR/X11DDW-L, BIOS 2.0a 12/06/2017 Workqueue: dm-thin do_worker [dm_thin_pool] Call Trace: dump_stack+0x5a/0x73 sysfs_warn_dup+0x58/0x70 sysfs_create_dir_ns+0x77/0x80 kobject_add_internal+0xba/0x2e0 kobject_init_and_add+0x70/0xb0 sysfs_slab_add+0xb1/0x250 __kmem_cache_create+0x116/0x150 create_cache+0xd9/0x1f0 kmem_cache_create_usercopy+0x1c1/0x250 kmem_cache_create+0x18/0x20 dm_bufio_client_create+0x1ae/0x410 [dm_bufio] dm_block_manager_create+0x5e/0x90 [dm_persistent_data] __create_persistent_data_objects+0x38/0x940 [dm_thin_pool] dm_pool_abort_metadata+0x64/0x90 [dm_thin_pool] metadata_operation_failed+0x59/0x100 [dm_thin_pool] alloc_data_block.isra.53+0x86/0x180 [dm_thin_pool] process_cell+0x2a3/0x550 [dm_thin_pool] do_worker+0x28d/0x8f0 [dm_thin_pool] process_one_work+0x171/0x370 worker_thread+0x49/0x3f0 kthread+0xf8/0x130 ret_from_fork+0x35/0x40 kobject_add_internal failed for :a-0000144 with -EEXIST, don't try to register things with the same name in the same directory. kmem_cache_create(dm_bufio_buffer-16) failed with error -17 Link: http://lkml.kernel.org/r/alpine.LRH.2.02.1806151817130.6333@file01.intranet.prod.int.rdu2.redhat.com Signed-off-by: Mikulas Patocka Reported-by: Mike Snitzer Tested-by: Mike Snitzer Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

kmemcheck: stop using GFP_NOTRACK and SLAB_NOTRACK

2018-02-22T14:42:23+00:00

commit 75f296d93bcebcfe375884ddac79e30263a31766 upstream. Convert all allocations that used a NOTRACK flag to stop using it. Link: http://lkml.kernel.org/r/20171007030159.22241-3-alexander.levin@verizon.com Signed-off-by: Sasha Levin Cc: Alexander Potapenko Cc: Eric W. Biederman Cc: Michal Hocko Cc: Pekka Enberg Cc: Steven Rostedt Cc: Tim Hansen Cc: Vegard Nossum Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

License cleanup: add SPDX GPL-2.0 license identifier to files with no license

2017-11-02T10:10:55+00:00

Many source files in the tree are missing licensing information, which makes it harder for compliance tools to determine the correct license. By default all files without license information are under the default license of the kernel, which is GPL version 2. Update the files which contain no license information with the 'GPL-2.0' SPDX license identifier. The SPDX identifier is a legally binding shorthand, which can be used instead of the full boiler plate text. This patch is based on work done by Thomas Gleixner and Kate Stewart and Philippe Ombredanne. How this work was done: Patches were generated and checked against linux-4.14-rc6 for a subset of the use cases: - file had no licensing information it it. - file was a */uapi/* one with no licensing information in it, - file was a */uapi/* one with existing licensing information, Further patches will be generated in subsequent months to fix up cases where non-standard license headers were used, and references to license had to be inferred by heuristics based on keywords. The analysis to determine which SPDX License Identifier to be applied to a file was done in a spreadsheet of side by side results from of the output of two independent scanners (ScanCode & Windriver) producing SPDX tag:value files created by Philippe Ombredanne. Philippe prepared the base worksheet, and did an initial spot review of a few 1000 files. The 4.13 kernel was the starting point of the analysis with 60,537 files assessed. Kate Stewart did a file by file comparison of the scanner results in the spreadsheet to determine which SPDX license identifier(s) to be applied to the file. She confirmed any determination that was not immediately clear with lawyers working with the Linux Foundation. Criteria used to select files for SPDX license identifier tagging was: - Files considered eligible had to be source code files. - Make and config files were included as candidates if they contained >5 lines of source - File already had some variant of a license header in it (even if <5 lines). All documentation files were explicitly excluded. The following heuristics were used to determine which SPDX license identifiers to apply. - when both scanners couldn't find any license traces, file was considered to have no license information in it, and the top level COPYING file license applied. For non */uapi/* files that summary was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 11139 and resulted in the first patch in this series. If that file was a */uapi/* path one, it was "GPL-2.0 WITH Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 WITH Linux-syscall-note 930 and resulted in the second patch in this series. - if a file had some form of licensing information in it, and was one of the */uapi/* ones, it was denoted with the Linux-syscall-note if any GPL family license was found in the file or had no licensing in it (per prior point). Results summary: SPDX license identifier # files ---------------------------------------------------|------ GPL-2.0 WITH Linux-syscall-note 270 GPL-2.0+ WITH Linux-syscall-note 169 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17 LGPL-2.1+ WITH Linux-syscall-note 15 GPL-1.0+ WITH Linux-syscall-note 14 ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5 LGPL-2.0+ WITH Linux-syscall-note 4 LGPL-2.1 WITH Linux-syscall-note 3 ((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3 ((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1 and that resulted in the third patch in this series. - when the two scanners agreed on the detected license(s), that became the concluded license(s). - when there was disagreement between the two scanners (one detected a license but the other didn't, or they both detected different licenses) a manual inspection of the file occurred. - In most cases a manual inspection of the information in the file resulted in a clear resolution of the license that should apply (and which scanner probably needed to revisit its heuristics). - When it was not immediately clear, the license identifier was confirmed with lawyers working with the Linux Foundation. - If there was any question as to the appropriate license identifier, the file was flagged for further research and to be revisited later in time. In total, over 70 hours of logged manual review was done on the spreadsheet to determine the SPDX license identifiers to apply to the source files by Kate, Philippe, Thomas and, in some cases, confirmation by lawyers working with the Linux Foundation. Kate also obtained a third independent scan of the 4.13 code base from FOSSology, and compared selected files where the other two scanners disagreed against that SPDX file, to see if there was new insights. The Windriver scanner is based on an older version of FOSSology in part, so they are related. Thomas did random spot checks in about 500 files from the spreadsheets for the uapi headers and agreed with SPDX license identifier in the files he inspected. For the non-uapi files Thomas did random spot checks in about 15000 files. In initial set of patches against 4.14-rc6, 3 files were found to have copy/paste license identifier errors, and have been fixed to reflect the correct identifier. Additionally Philippe spent 10 hours this week doing a detailed manual inspection and review of the 12,461 patched files from the initial patch version early this week with: - a full scancode scan run, collecting the matched texts, detected license ids and scores - reviewing anything where there was a license detected (about 500+ files) to ensure that the applied SPDX license was correct - reviewing anything where there was no detection but the patch license was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied SPDX license was correct This produced a worksheet with 20 files needing minor correction. This worksheet was then exported into 3 different .csv files for the different types of files to be modified. These .csv files were then reviewed by Greg. Thomas wrote a script to parse the csv files and add the proper SPDX tag to the file, in the format that the file expected. This script was further refined by Greg based on the output to detect more types of files automatically and to distinguish between header and source .c files (which need different comment types.) Finally Greg ran the script using the .csv files to generate the patches. Reviewed-by: Kate Stewart Reviewed-by: Philippe Ombredanne Reviewed-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman

mm: memcontrol: use vmalloc fallback for large kmem memcg arrays

2017-10-04T00:54:25+00:00

For quick per-memcg indexing, slab caches and list_lru structures maintain linear arrays of descriptors. As the number of concurrent memory cgroups in the system goes up, this requires large contiguous allocations (8k cgroups = order-5, 16k cgroups = order-6 etc.) for every existing slab cache and list_lru, which can easily fail on loaded systems. E.g.: mkdir: page allocation failure: order:5, mode:0x14040c0(GFP_KERNEL|__GFP_COMP), nodemask=(null) CPU: 1 PID: 6399 Comm: mkdir Not tainted 4.13.0-mm1-00065-g720bbe532b7c-dirty #481 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-20170228_101828-anatol 04/01/2014 Call Trace: ? __alloc_pages_direct_compact+0x4c/0x110 __alloc_pages_nodemask+0xf50/0x1430 alloc_pages_current+0x60/0xc0 kmalloc_order_trace+0x29/0x1b0 __kmalloc+0x1f4/0x320 memcg_update_all_list_lrus+0xca/0x2e0 mem_cgroup_css_alloc+0x612/0x670 cgroup_apply_control_enable+0x19e/0x360 cgroup_mkdir+0x322/0x490 kernfs_iop_mkdir+0x55/0x80 vfs_mkdir+0xd0/0x120 SyS_mkdirat+0x6c/0xe0 SyS_mkdir+0x14/0x20 entry_SYSCALL_64_fastpath+0x18/0xad Mem-Info: active_anon:2965 inactive_anon:19 isolated_anon:0 active_file:100270 inactive_file:98846 isolated_file:0 unevictable:0 dirty:0 writeback:0 unstable:0 slab_reclaimable:7328 slab_unreclaimable:16402 mapped:771 shmem:52 pagetables:278 bounce:0 free:13718 free_pcp:0 free_cma:0 This output is from an artificial reproducer, but we have repeatedly observed order-7 failures in production in the Facebook fleet. These systems become useless as they cannot run more jobs, even though there is plenty of memory to allocate 128 individual pages. Use kvmalloc and kvzalloc to fall back to vmalloc space if these arrays prove too large for allocating them physically contiguous. Link: http://lkml.kernel.org/r/20170918184919.20644-1-hannes@cmpxchg.org Signed-off-by: Johannes Weiner Reviewed-by: Josef Bacik Acked-by: Michal Hocko Acked-by: Vladimir Davydov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: allow slab_nomerge to be set at build time

2017-07-06T23:24:31+00:00

Some hardened environments want to build kernels with slab_nomerge already set (so that they do not depend on remembering to set the kernel command line option). This is desired to reduce the risk of kernel heap overflows being able to overwrite objects from merged caches and changes the requirements for cache layout control, increasing the difficulty of these attacks. By keeping caches unmerged, these kinds of exploits can usually only damage objects in the same cache (though the risk to metadata exploitation is unchanged). Link: http://lkml.kernel.org/r/20170620230911.GA25238@beast Signed-off-by: Kees Cook Cc: Daniel Micay Cc: David Windsor Cc: Eric Biggers Cc: Christoph Lameter Cc: Jonathan Corbet Cc: Daniel Micay Cc: David Windsor Cc: Eric Biggers Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Cc: "Rafael J. Wysocki" Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Mauro Carvalho Chehab Cc: "Paul E. McKenney" Cc: Arnd Bergmann Cc: Andy Lutomirski Cc: Nicolas Pitre Cc: Tejun Heo Cc: Daniel Mack Cc: Sebastian Andrzej Siewior Cc: Sergey Senozhatsky Cc: Helge Deller Cc: Rik van Riel Cc: Randy Dunlap Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: Rename SLAB_DESTROY_BY_RCU to SLAB_TYPESAFE_BY_RCU

2017-04-18T18:42:36+00:00

A group of Linux kernel hackers reported chasing a bug that resulted from their assumption that SLAB_DESTROY_BY_RCU provided an existence guarantee, that is, that no block from such a slab would be reallocated during an RCU read-side critical section. Of course, that is not the case. Instead, SLAB_DESTROY_BY_RCU only prevents freeing of an entire slab of blocks. However, there is a phrase for this, namely "type safety". This commit therefore renames SLAB_DESTROY_BY_RCU to SLAB_TYPESAFE_BY_RCU in order to avoid future instances of this sort of confusion. Signed-off-by: Paul E. McKenney Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Cc: Andrew Morton Cc: Acked-by: Johannes Weiner Acked-by: Vlastimil Babka [ paulmck: Add comments mentioning the old name, as requested by Eric Dumazet, in order to help people familiar with the old name find the new one. ] Acked-by: David Rientjes

kasan: drain quarantine of memcg slab objects

2017-02-25T01:46:56+00:00

Per memcg slab accounting and kasan have a problem with kmem_cache destruction. - kmem_cache_create() allocates a kmem_cache, which is used for allocations from processes running in root (top) memcg. - Processes running in non root memcg and allocating with either __GFP_ACCOUNT or from a SLAB_ACCOUNT cache use a per memcg kmem_cache. - Kasan catches use-after-free by having kfree() and kmem_cache_free() defer freeing of objects. Objects are placed in a quarantine. - kmem_cache_destroy() destroys root and non root kmem_caches. It takes care to drain the quarantine of objects from the root memcg's kmem_cache, but ignores objects associated with non root memcg. This causes leaks because quarantined per memcg objects refer to per memcg kmem cache being destroyed. To see the problem: 1) create a slab cache with kmem_cache_create(,,,SLAB_ACCOUNT,) 2) from non root memcg, allocate and free a few objects from cache 3) dispose of the cache with kmem_cache_destroy() kmem_cache_destroy() will trigger a "Slab cache still has objects" warning indicating that the per memcg kmem_cache structure was leaked. Fix the leak by draining kasan quarantined objects allocated from non root memcg. Racing memcg deletion is tricky, but handled. kmem_cache_destroy() => shutdown_memcg_caches() => __shutdown_memcg_cache() => shutdown_cache() flushes per memcg quarantined objects, even if that memcg has been rmdir'd and gone through memcg_deactivate_kmem_caches(). This leak only affects destroyed SLAB_ACCOUNT kmem caches when kasan is enabled. So I don't think it's worth patching stable kernels. Link: http://lkml.kernel.org/r/1482257462-36948-1-git-send-email-gthelen@google.com Signed-off-by: Greg Thelen Reviewed-by: Vladimir Davydov Acked-by: Andrey Ryabinin Cc: Alexander Potapenko Cc: Dmitry Vyukov Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

slab: use memcg_kmem_cache_wq for slab destruction operations

2017-02-23T00:41:27+00:00

If there's contention on slab_mutex, queueing the per-cache destruction work item on the system_wq can unnecessarily create and tie up a lot of kworkers. Rename memcg_kmem_cache_create_wq to memcg_kmem_cache_wq and make it global and use that workqueue for the destruction work items too. While at it, convert the workqueue from an unbound workqueue to a per-cpu one with concurrency limited to 1. It's generally preferable to use per-cpu workqueues and concurrency limit of 1 is safe enough. This is suggested by Joonsoo Kim. Link: http://lkml.kernel.org/r/20170117235411.9408-11-tj@kernel.org Signed-off-by: Tejun Heo Reported-by: Jay Vana Acked-by: Vladimir Davydov Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds