Bug 2297533 (CVE-2024-40949) - CVE-2024-40949 kernel: mm: shmem: fix getting incorrect lruvec when replacing a shmem folio
Summary: CVE-2024-40949 kernel: mm: shmem: fix getting incorrect lruvec when replacing...
Keywords:
Status: NEW
Alias: CVE-2024-40949
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Product Security DevOps Team
QA Contact:
URL:
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Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2024-07-12 13:38 UTC by OSIDB Bzimport
Modified: 2024-09-27 23:32 UTC (History)
4 users (show)

Fixed In Version: kernel 6.9.7, kernel 6.10-rc5
Doc Type: If docs needed, set a value
Doc Text:
A flaw was found in "mm: shmem" in the Linux Kernel. This issue was resolved by fixing incorrect LRU vector handling when replacing shmem folios. The issue occurred because the replacement cleared the old folio's memory control group (memcg) data, causing incorrect LRU vector retrieval and potential system crashes due to wrong LRU locks and inaccurate statistics.
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Description OSIDB Bzimport 2024-07-12 13:38:41 UTC 
In the Linux kernel, the following vulnerability has been resolved:

mm: shmem: fix getting incorrect lruvec when replacing a shmem folio

When testing shmem swapin, I encountered the warning below on my machine. 
The reason is that replacing an old shmem folio with a new one causes
mem_cgroup_migrate() to clear the old folio's memcg data.  As a result,
the old folio cannot get the correct memcg's lruvec needed to remove
itself from the LRU list when it is being freed.  This could lead to
possible serious problems, such as LRU list crashes due to holding the
wrong LRU lock, and incorrect LRU statistics.

To fix this issue, we can fallback to use the mem_cgroup_replace_folio()
to replace the old shmem folio.

[ 5241.100311] page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x5d9960
[ 5241.100317] head: order:4 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
[ 5241.100319] flags: 0x17fffe0000040068(uptodate|lru|head|swapbacked|node=0|zone=2|lastcpupid=0x3ffff)
[ 5241.100323] raw: 17fffe0000040068 fffffdffd6687948 fffffdffd69ae008 0000000000000000
[ 5241.100325] raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
[ 5241.100326] head: 17fffe0000040068 fffffdffd6687948 fffffdffd69ae008 0000000000000000
[ 5241.100327] head: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
[ 5241.100328] head: 17fffe0000000204 fffffdffd6665801 ffffffffffffffff 0000000000000000
[ 5241.100329] head: 0000000a00000010 0000000000000000 00000000ffffffff 0000000000000000
[ 5241.100330] page dumped because: VM_WARN_ON_ONCE_FOLIO(!memcg && !mem_cgroup_disabled())
[ 5241.100338] ------------[ cut here ]------------
[ 5241.100339] WARNING: CPU: 19 PID: 78402 at include/linux/memcontrol.h:775 folio_lruvec_lock_irqsave+0x140/0x150
[...]
[ 5241.100374] pc : folio_lruvec_lock_irqsave+0x140/0x150
[ 5241.100375] lr : folio_lruvec_lock_irqsave+0x138/0x150
[ 5241.100376] sp : ffff80008b38b930
[...]
[ 5241.100398] Call trace:
[ 5241.100399]  folio_lruvec_lock_irqsave+0x140/0x150
[ 5241.100401]  __page_cache_release+0x90/0x300
[ 5241.100404]  __folio_put+0x50/0x108
[ 5241.100406]  shmem_replace_folio+0x1b4/0x240
[ 5241.100409]  shmem_swapin_folio+0x314/0x528
[ 5241.100411]  shmem_get_folio_gfp+0x3b4/0x930
[ 5241.100412]  shmem_fault+0x74/0x160
[ 5241.100414]  __do_fault+0x40/0x218
[ 5241.100417]  do_shared_fault+0x34/0x1b0
[ 5241.100419]  do_fault+0x40/0x168
[ 5241.100420]  handle_pte_fault+0x80/0x228
[ 5241.100422]  __handle_mm_fault+0x1c4/0x440
[ 5241.100424]  handle_mm_fault+0x60/0x1f0
[ 5241.100426]  do_page_fault+0x120/0x488
[ 5241.100429]  do_translation_fault+0x4c/0x68
[ 5241.100431]  do_mem_abort+0x48/0xa0
[ 5241.100434]  el0_da+0x38/0xc0
[ 5241.100436]  el0t_64_sync_handler+0x68/0xc0
[ 5241.100437]  el0t_64_sync+0x14c/0x150
[ 5241.100439] ---[ end trace 0000000000000000 ]---

[baolin.wang.com: remove less helpful comments, per Matthew]
  Link: https://lkml.kernel.org/r/ccad3fe1375b468ebca3227b6b729f3eaf9d8046.1718423197.git.baolin.wang@linux.alibaba.com
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