linux-stable.git/fs/proc, branch linux-6.8.y

fs/proc/task_mmu: fix uffd-wp confusion in pagemap_scan_pmd_entry()

2024-05-17T10:15:09+00:00

commit 2c7ad9a590d1a99ec59c7d90cef41e2b296944c4 upstream.

pagemap_scan_pmd_entry() checks if uffd-wp is set on each pte to avoid
unnecessary if set.  However it was previously checking with
`pte_uffd_wp(ptep_get(pte))` without first confirming that the pte was
present.  It is only valid to call pte_uffd_wp() for present ptes.  For
swap ptes, pte_swp_uffd_wp() must be called because the uffd-wp bit may be
kept in a different position, depending on the arch.

This was leading to test failures in the pagemap_ioctl mm selftest, when
bringing up uffd-wp support on arm64 due to incorrectly interpretting the
uffd-wp status of migration entries.

Let's fix this by using the correct check based on pte_present().  While
we are at it, let's pass the pte to make_uffd_wp_pte() to avoid the
pointless extra ptep_get() which can't be optimized out due to READ_ONCE()
on many arches.

Link: https://lkml.kernel.org/r/20240429114104.182890-1-ryan.roberts@arm.com
Fixes: 12f6b01a0bcb ("fs/proc/task_mmu: add fast paths to get/clear PAGE_IS_WRITTEN flag")
Closes: https://lore.kernel.org/linux-arm-kernel/ZiuyGXt0XWwRgFh9@x1n/
Signed-off-by: Ryan Roberts 
Acked-by: David Hildenbrand 
Reviewed-by: Muhammad Usama Anjum 
Tested-by: Muhammad Usama Anjum 
Cc: Peter Xu 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Greg Kroah-Hartman

fs/proc/task_mmu: fix loss of young/dirty bits during pagemap scan

2024-05-17T10:15:08+00:00

commit c70dce4982ce1718bf978a35f8e26160b82081f4 upstream.

make_uffd_wp_pte() was previously doing:

  pte = ptep_get(ptep);
  ptep_modify_prot_start(ptep);
  pte = pte_mkuffd_wp(pte);
  ptep_modify_prot_commit(ptep, pte);

But if another thread accessed or dirtied the pte between the first 2
calls, this could lead to loss of that information.  Since
ptep_modify_prot_start() gets and clears atomically, the following is the
correct pattern and prevents any possible race.  Any access after the
first call would see an invalid pte and cause a fault:

  pte = ptep_modify_prot_start(ptep);
  pte = pte_mkuffd_wp(pte);
  ptep_modify_prot_commit(ptep, pte);

Link: https://lkml.kernel.org/r/20240429114017.182570-1-ryan.roberts@arm.com
Fixes: 52526ca7fdb9 ("fs/proc/task_mmu: implement IOCTL to get and optionally clear info about PTEs")
Signed-off-by: Ryan Roberts 
Acked-by: David Hildenbrand 
Cc: Muhammad Usama Anjum 
Cc: Peter Xu 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Greg Kroah-Hartman

mm: support page_mapcount() on page_has_type() pages

2024-05-02T14:35:26+00:00

commit fd1a745ce03e37945674c14833870a9af0882e2d upstream.

Return 0 for pages which can't be mapped.  This matches how page_mapped()
works.  It is more convenient for users to not have to filter out these
pages.

Link: https://lkml.kernel.org/r/20240321142448.1645400-5-willy@infradead.org
Fixes: 9c5ccf2db04b ("mm: remove HUGETLB_PAGE_DTOR")
Signed-off-by: Matthew Wilcox (Oracle) 
Reviewed-by: David Hildenbrand 
Acked-by: Vlastimil Babka 
Cc: Miaohe Lin 
Cc: Muchun Song 
Cc: Oscar Salvador 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Greg Kroah-Hartman

fs/proc: Skip bootloader comment if no embedded kernel parameters

2024-04-17T09:23:36+00:00

commit c722cea208789d9e2660992bcd05fb9fac3adb56 upstream.

If the "bootconfig" kernel command-line argument was specified or if
the kernel was built with CONFIG_BOOT_CONFIG_FORCE, but if there are
no embedded kernel parameter, omit the "# Parameters from bootloader:"
comment from the /proc/bootconfig file.  This will cause automation
to fall back to the /proc/cmdline file, which will be identical to the
comment in this no-embedded-kernel-parameters case.

Link: https://lore.kernel.org/all/20240409044358.1156477-2-paulmck@kernel.org/

Fixes: 8b8ce6c75430 ("fs/proc: remove redundant comments from /proc/bootconfig")
Signed-off-by: Masami Hiramatsu 
Signed-off-by: Paul E. McKenney 
Cc: stable@vger.kernel.org
Acked-by: Masami Hiramatsu (Google) 
Signed-off-by: Masami Hiramatsu (Google) 
Signed-off-by: Greg Kroah-Hartman

fs/proc: remove redundant comments from /proc/bootconfig

2024-04-17T09:23:36+00:00

commit fbbdc255fbee59b4207a5398fdb4f04590681a79 upstream.

commit 717c7c894d4b ("fs/proc: Add boot loader arguments as comment to
/proc/bootconfig") adds bootloader argument comments into /proc/bootconfig.

/proc/bootconfig shows boot_command_line[] multiple times following
every xbc key value pair, that's duplicated and not necessary.
Remove redundant ones.

Output before and after the fix is like:
key1 = value1
*bootloader argument comments*
key2 = value2
*bootloader argument comments*
key3 = value3
*bootloader argument comments*
...

key1 = value1
key2 = value2
key3 = value3
*bootloader argument comments*
...

Link: https://lore.kernel.org/all/20240409044358.1156477-1-paulmck@kernel.org/

Fixes: 717c7c894d4b ("fs/proc: Add boot loader arguments as comment to /proc/bootconfig")
Signed-off-by: Zhenhua Huang 
Signed-off-by: Paul E. McKenney 
Cc: 
Cc: 
Cc: stable@vger.kernel.org
Acked-by: Masami Hiramatsu (Google) 
Signed-off-by: Masami Hiramatsu (Google) 
Signed-off-by: Greg Kroah-Hartman

kbuild: make -Woverride-init warnings more consistent

2024-04-10T14:38:00+00:00

[ Upstream commit c40845e3195d074b34f8f8e400e28c9403a06588 ]

The -Woverride-init warn about code that may be intentional or not,
but the inintentional ones tend to be real bugs, so there is a bit of
disagreement on whether this warning option should be enabled by default
and we have multiple settings in scripts/Makefile.extrawarn as well as
individual subsystems.

Older versions of clang only supported -Wno-initializer-overrides with
the same meaning as gcc's -Woverride-init, though all supported versions
now work with both. Because of this difference, an earlier cleanup of
mine accidentally turned the clang warning off for W=1 builds and only
left it on for W=2, while it's still enabled for gcc with W=1.

There is also one driver that only turns the warning off for newer
versions of gcc but not other compilers, and some but not all the
Makefiles still use a cc-disable-warning conditional that is no
longer needed with supported compilers here.

Address all of the above by removing the special cases for clang
and always turning the warning off unconditionally where it got
in the way, using the syntax that is supported by both compilers.

Fixes: 2cd3271b7a31 ("kbuild: avoid duplicate warning options")
Signed-off-by: Arnd Bergmann 
Acked-by: Hamza Mahfooz 
Acked-by: Jani Nikula 
Acked-by: Andrew Jeffery 
Signed-off-by: Jani Nikula 
Reviewed-by: Linus Walleij 
Signed-off-by: Masahiro Yamada 
Signed-off-by: Sasha Levin

Merge tag 'pull-fixes.pathwalk-rcu-2' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

2024-02-25T17:29:05+00:00

Pull RCU pathwalk fixes from Al Viro:
 "We still have some races in filesystem methods when exposed to RCU
  pathwalk. This series is a result of code audit (the second round of
  it) and it should deal with most of that stuff.

  Still pending: ntfs3 ->d_hash()/->d_compare() and ceph_d_revalidate().
  Up to maintainers (a note for NTFS folks - when documentation says
  that a method may not block, it *does* imply that blocking allocations
  are to be avoided. Really)"

[ More explanations for people who aren't familiar with the vagaries of
  RCU path walking: most of it is hidden from filesystems, but if a
  filesystem actively participates in the low-level path walking it
  needs to make sure the fields involved in that walk are RCU-safe.

  That "actively participate in low-level path walking" includes things
  like having its own ->d_hash()/->d_compare() routines, or by having
  its own directory permission function that doesn't just use the common
  helpers.  Having a ->d_revalidate() function will also have this issue.

  Note that instead of making everything RCU safe you can also choose to
  abort the RCU pathwalk if your operation cannot be done safely under
  RCU, but that obviously comes with a performance penalty. One common
  pattern is to allow the simple cases under RCU, and abort only if you
  need to do something more complicated.

  So not everything needs to be RCU-safe, and things like the inode etc
  that the VFS itself maintains obviously already are. But these fixes
  tend to be about properly RCU-delaying things like ->s_fs_info that
  are maintained by the filesystem and that got potentially released too
  early.   - Linus ]

* tag 'pull-fixes.pathwalk-rcu-2' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  ext4_get_link(): fix breakage in RCU mode
  cifs_get_link(): bail out in unsafe case
  fuse: fix UAF in rcu pathwalks
  procfs: make freeing proc_fs_info rcu-delayed
  procfs: move dropping pde and pid from ->evict_inode() to ->free_inode()
  nfs: fix UAF on pathwalk running into umount
  nfs: make nfs_set_verifier() safe for use in RCU pathwalk
  afs: fix __afs_break_callback() / afs_drop_open_mmap() race
  hfsplus: switch to rcu-delayed unloading of nls and freeing ->s_fs_info
  exfat: move freeing sbi, upcase table and dropping nls into rcu-delayed helper
  affs: free affs_sb_info with kfree_rcu()
  rcu pathwalk: prevent bogus hard errors from may_lookup()
  fs/super.c: don't drop ->s_user_ns until we free struct super_block itself

procfs: make freeing proc_fs_info rcu-delayed

2024-02-25T07:10:32+00:00

makes proc_pid_ns() safe from rcu pathwalk (put_pid_ns()
is still synchronous, but that's not a problem - it does
rcu-delay everything that needs to be)

Reviewed-by: Christian Brauner 
Signed-off-by: Al Viro

procfs: move dropping pde and pid from ->evict_inode() to ->free_inode()

2024-02-25T07:10:32+00:00

that keeps both around until struct inode is freed, making access
to them safe from rcu-pathwalk

Acked-by: Christian Brauner 
Signed-off-by: Al Viro

fs/proc: do_task_stat: use sig->stats_lock to gather the threads/children stats

2024-02-08T05:20:33+00:00

lock_task_sighand() can trigger a hard lockup.  If NR_CPUS threads call
do_task_stat() at the same time and the process has NR_THREADS, it will
spin with irqs disabled O(NR_CPUS * NR_THREADS) time.

Change do_task_stat() to use sig->stats_lock to gather the statistics
outside of ->siglock protected section, in the likely case this code will
run lockless.

Link: https://lkml.kernel.org/r/20240123153357.GA21857@redhat.com
Signed-off-by: Oleg Nesterov 
Signed-off-by: Dylan Hatch 
Cc: Eric W. Biederman 
Cc: 
Signed-off-by: Andrew Morton