Subject: CVE-2024-36882: mm: use memalloc_nofs_save() in page_cache_ra_order()

From: Greg Kroah-Hartman <[email-masked]>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

mm: use memalloc_nofs_save() in page_cache_ra_order()

See commit f2c817bed58d ("mm: use memalloc_nofs_save in readahead path"),
ensure that page_cache_ra_order() do not attempt to reclaim file-backed
pages too, or it leads to a deadlock, found issue when test ext4 large
folio.

 INFO: task DataXceiver for:7494 blocked for more than 120 seconds.
 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
 task:DataXceiver for state:D stack:0     pid:7494  ppid:1      flags:0x00000200
 Call trace:
  __switch_to+0x14c/0x240
  __schedule+0x82c/0xdd0
  schedule+0x58/0xf0
  io_schedule+0x24/0xa0
  __folio_lock+0x130/0x300
  migrate_pages_batch+0x378/0x918
  migrate_pages+0x350/0x700
  compact_zone+0x63c/0xb38
  compact_zone_order+0xc0/0x118
  try_to_compact_pages+0xb0/0x280
  __alloc_pages_direct_compact+0x98/0x248
  __alloc_pages+0x510/0x1110
  alloc_pages+0x9c/0x130
  folio_alloc+0x20/0x78
  filemap_alloc_folio+0x8c/0x1b0
  page_cache_ra_order+0x174/0x308
  ondemand_readahead+0x1c8/0x2b8
  page_cache_async_ra+0x68/0xb8
  filemap_readahead.isra.0+0x64/0xa8
  filemap_get_pages+0x3fc/0x5b0
  filemap_splice_read+0xf4/0x280
  ext4_file_splice_read+0x2c/0x48 [ext4]
  vfs_splice_read.part.0+0xa8/0x118
  splice_direct_to_actor+0xbc/0x288
  do_splice_direct+0x9c/0x108
  do_sendfile+0x328/0x468
  __arm64_sys_sendfile64+0x8c/0x148
  invoke_syscall+0x4c/0x118
  el0_svc_common.constprop.0+0xc8/0xf0
  do_el0_svc+0x24/0x38
  el0_svc+0x4c/0x1f8
  el0t_64_sync_handler+0xc0/0xc8
  el0t_64_sync+0x188/0x190

The Linux kernel CVE team has assigned CVE-2024-36882 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 5.18 with commit 793917d997df and fixed in 6.1.91 with commit 7629ef6dda15
	Issue introduced in 5.18 with commit 793917d997df and fixed in 6.6.31 with commit 468971c3f4b8
	Issue introduced in 5.18 with commit 793917d997df and fixed in 6.8.10 with commit cf6a1d16c6df
	Issue introduced in 5.18 with commit 793917d997df and fixed in 6.9 with commit 30153e446664

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2024-36882
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	mm/readahead.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/7629ef6dda1564098aadeef38e5fbd11ee8627c4
	https://git.kernel.org/stable/c/468971c3f4b8187f25334503b68050a0e1370147
	https://git.kernel.org/stable/c/cf6a1d16c6df3c30b03f0c6a92a2ba7f86dffb45
	https://git.kernel.org/stable/c/30153e4466647a17eebfced13eede5cbe4290e69