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Linus Torvalds 5f0bc0b042 mm: suppress mm fault logging if fatal signal already pending 
Commit eda0047296 ("mm: make the page fault mmap locking killable")
intentionally made it much easier to trigger the "page fault fails
because a fatal signal is pending" situation, by having the mmap locking
fail early in that case.

We have long aborted page faults in other fatal cases when the actual IO
for a page is interrupted by SIGKILL - which is particularly useful for
the traditional case of NFS hanging due to network issues, but local
filesystems could cause it too if you happened to get the SIGKILL while
waiting for a page to be faulted in (eg lock_folio_maybe_drop_mmap()).

So aborting the page fault wasn't a new condition - but it now triggers
earlier, before we even get to 'handle_mm_fault()'.  And as a result the
error doesn't go through our 'fault_signal_pending()' logic, and doesn't
get filtered away there.

Normally you'd never even notice, because if a fatal signal is pending,
the new SIGSEGV we send ends up being ignored anyway.

But it turns out that there is one very noticeable exception: if you
enable 'show_unhandled_signals', the aborted page fault will be logged
in the kernel messages, and you'll get a scary line looking something
like this in your logs:

  pverados[2183248]: segfault at 55e5a00f9ae0 ip 000055e5a00f9ae0 sp 00007ffc0720bea8 error 14 in perl[55e5a00d4000+195000] likely on CPU 10 (core 4, socket 0)

which is rather misleading.  It's not really a segfault at all, it's
just "the thread was killed before the page fault completed, so we
aborted the page fault".

Fix this by just making it clear that a pending fatal signal means that
any new signal coming in after that is implicitly handled.  This will
avoid the misleading logging, since now the signal isn't 'unhandled' any
more.

Reported-and-tested-by: Fiona Ebner <f.ebner@proxmox.com>
Tested-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
Link: https://lore.kernel.org/lkml/8d063a26-43f5-0bb7-3203-c6a04dc159f8@proxmox.com/
Acked-by: Oleg Nesterov <oleg@redhat.com>
Fixes: eda0047296 ("mm: make the page fault mmap locking killable")
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 		2023-07-26 10:51:59 -07:00
Documentation Devicetree fixes for v6.5: 2023-07-22 10:28:22 -07:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
arch x86/traps: Fix load_unaligned_zeropad() handling for shared TDX memory 2023-07-25 15:29:01 -07:00
block block-6.5-2023-07-21 2023-07-22 11:05:15 -07:00
certs KEYS: Add missing function documentation 2023-04-24 16:15:52 +03:00
crypto crypto: algif_hash - Fix race between MORE and non-MORE sends 2023-07-08 22:48:42 +10:00
drivers SCSI fixes on 20230724 2023-07-24 14:38:41 -07:00
fs ovl: Always reevaluate the file signature for IMA 2023-07-25 15:36:22 -07:00
include ARM: 2023-07-23 10:44:38 -07:00
init Kbuild updates for v6.5 2023-07-01 09:24:31 -07:00
io_uring io_uring-6.5-2023-07-21 2023-07-22 10:46:30 -07:00
ipc Merge branch 'work.namespace' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2023-02-24 19:20:07 -08:00
kernel mm: suppress mm fault logging if fatal signal already pending 2023-07-26 10:51:59 -07:00
lib block-6.5-2023-07-21 2023-07-22 11:05:15 -07:00
mm mm/mlock: fix vma iterator conversion of apply_vma_lock_flags() 2023-07-17 12:53:21 -07:00
net Including fixes from BPF, netfilter, bluetooth and CAN. 2023-07-20 14:46:39 -07:00
rust rust: error: `impl Debug` for `Error` with `errname()` integration 2023-06-13 01:24:42 +02:00
samples arm64: ftrace: Add direct call trampoline samples support 2023-07-10 17:51:54 -04:00
scripts Kbuild fixes for v6.5 2023-07-23 14:55:41 -07:00
security security: keys: Modify mismatched function name 2023-07-17 19:40:27 +00:00
sound ASoC: Fixes for v6.5 2023-07-20 15:16:11 +02:00
tools sound fixes for 6.5-rc3 2023-07-21 10:10:18 -07:00
usr initramfs: Encode dependency on KBUILD_BUILD_TIMESTAMP 2023-06-06 17:54:49 +09:00
virt ARM64: 2023-07-03 15:32:22 -07:00
.clang-format iommu: Add for_each_group_device() 2023-05-23 08:15:51 +02:00
.cocciconfig
…
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore Revert ".gitignore: ignore *.cover and *.mbx" 2023-07-04 15:05:12 -07:00
.mailmap Including fixes from BPF, netfilter, bluetooth and CAN. 2023-07-20 14:46:39 -07:00
.rustfmt.toml rust: add `.rustfmt.toml` 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS - Address -Wmissing-prototype warnings 2023-06-26 16:43:54 -07:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Linux 6.5-rc2 2023-07-17 06:12:31 +01:00
Makefile Linux 6.5-rc3 2023-07-23 15:24:10 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.