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Mark Rutland 7e1088760c locking/atomic: sparc: Fix arch_cmpxchg64_local() 
Anatoly reports that since commit:

  ff5b4f1ed5 ("locking/atomic: sparc: move to ARCH_ATOMIC")

... it's possible to reliably trigger an oops by running:

  stress-ng -v --mmap 1 -t 30s

... which results in a NULL pointer dereference in
__split_huge_pmd_locked().

The underlying problem is that commit ff5b4f1ed5 left
arch_cmpxchg64_local() defined in terms of cmpxchg_local() rather than
arch_cmpxchg_local(). In <asm-generic/atomic-instrumented.h> we wrap
these with macros which use identically-named variables. When
cmpxchg_local() nests inside cmpxchg64_local(), this casues it to use an
unitialized variable as the pointer, which can be NULL.

This can also be seen in pmdp_establish(), where the compiler can
generate the pointer with a `clr` instruction:

0000000000000360 <pmdp_establish>:
 360:   9d e3 bf 50     save  %sp, -176, %sp
 364:   fa 5e 80 00     ldx  [ %i2 ], %i5
 368:   82 10 00 1b     mov  %i3, %g1
 36c:   84 10 20 00     clr  %g2
 370:   c3 f0 90 1d     casx  [ %g2 ], %i5, %g1
 374:   80 a7 40 01     cmp  %i5, %g1
 378:   32 6f ff fc     bne,a   %xcc, 368 <pmdp_establish+0x8>
 37c:   fa 5e 80 00     ldx  [ %i2 ], %i5
 380:   d0 5e 20 40     ldx  [ %i0 + 0x40 ], %o0
 384:   96 10 00 1b     mov  %i3, %o3
 388:   94 10 00 1d     mov  %i5, %o2
 38c:   92 10 00 19     mov  %i1, %o1
 390:   7f ff ff 84     call  1a0 <__set_pmd_acct>
 394:   b0 10 00 1d     mov  %i5, %i0
 398:   81 cf e0 08     return  %i7 + 8
 39c:   01 00 00 00     nop

This patch fixes the problem by defining arch_cmpxchg64_local() in terms
of arch_cmpxchg_local(), avoiding potential shadowing, and resulting in
working cmpxchg64_local() and variants, e.g.

0000000000000360 <pmdp_establish>:
 360:   9d e3 bf 50     save  %sp, -176, %sp
 364:   fa 5e 80 00     ldx  [ %i2 ], %i5
 368:   82 10 00 1b     mov  %i3, %g1
 36c:   c3 f6 90 1d     casx  [ %i2 ], %i5, %g1
 370:   80 a7 40 01     cmp  %i5, %g1
 374:   32 6f ff fd     bne,a   %xcc, 368 <pmdp_establish+0x8>
 378:   fa 5e 80 00     ldx  [ %i2 ], %i5
 37c:   d0 5e 20 40     ldx  [ %i0 + 0x40 ], %o0
 380:   96 10 00 1b     mov  %i3, %o3
 384:   94 10 00 1d     mov  %i5, %o2
 388:   92 10 00 19     mov  %i1, %o1
 38c:   7f ff ff 85     call  1a0 <__set_pmd_acct>
 390:   b0 10 00 1d     mov  %i5, %i0
 394:   81 cf e0 08     return  %i7 + 8
 398:   01 00 00 00     nop
 39c:   01 00 00 00     nop

Fixes: ff5b4f1ed5 ("locking/atomic: sparc: move to ARCH_ATOMIC")
Reported-by: Anatoly Pugachev <matorola@gmail.com>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Anatoly Pugachev <matorola@gmail.com>
Link: https://lore.kernel.org/r/20210707083032.567-1-mark.rutland@arm.com
 		2021-07-07 10:47:21 +02:00
Documentation Changes in this cycle were: 2021-06-28 13:30:02 -07:00
LICENSES LICENSES: Add the CC-BY-4.0 license 2020-12-08 10:33:27 -07:00
arch locking/atomic: sparc: Fix arch_cmpxchg64_local() 2021-07-07 10:47:21 +02:00
block sched: Change task_struct::state 2021-06-18 11:43:09 +02:00
certs Kbuild updates for v5.13 (2nd) 2021-05-08 10:00:11 -07:00
crypto async_xor: check src_offs is not NULL before updating it 2021-06-10 19:40:14 -07:00
drivers Scheduler udpates for this cycle: 2021-06-28 12:14:19 -07:00
fs Scheduler udpates for this cycle: 2021-06-28 12:14:19 -07:00
include Updates to the tick/nohz code in this cycle: 2021-06-28 12:22:06 -07:00
init sched: Change task_struct::state 2021-06-18 11:43:09 +02:00
ipc ipc/mqueue, msg, sem: avoid relying on a stack reference past its expiry 2021-05-22 15:09:07 -10:00
kernel kprobe/static_call: Restore missing static_call_text_reserved() 2021-07-05 10:47:16 +02:00
lib Scheduler udpates for this cycle: 2021-06-28 12:14:19 -07:00
mm Scheduler udpates for this cycle: 2021-06-28 12:14:19 -07:00
net Scheduler udpates for this cycle: 2021-06-28 12:14:19 -07:00
samples Perf events updates for this cycle: 2021-06-28 12:03:20 -07:00
scripts Locking changes for this cycle: 2021-06-28 11:45:29 -07:00
security trusted-keys: match tpm_get_ops on all return paths 2021-05-12 22:36:37 +03:00
sound spi: Updates for v5.14 2021-06-28 11:10:20 -07:00
tools Changes for this cycle: 2021-06-28 12:57:11 -07:00
usr .gitignore: prefix local generated files with a slash 2021-05-02 00:43:35 +09:00
virt Scheduler udpates for this cycle: 2021-06-28 12:14:19 -07:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap mailmap: add Marek's other e-mail address and identity without diacritics 2021-06-24 19:40:54 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: move Murali Karicheri to credits 2021-04-29 15:47:30 -07:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Updates to the tick/nohz code in this cycle: 2021-06-28 12:22:06 -07:00
Makefile Linux 5.13 2021-06-27 15:21:11 -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.