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[v3,0/2] Two x86 fixes

Message ID 20220301081133.106875-1-ammarfaizi2@gnuweeb.org
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Series Two x86 fixes | expand

Message

Ammar Faizi March 1, 2022, 8:11 a.m. UTC 
Hi,

Two fixes for x86 arch.

## Changelog
v3:
  - Fold in changes from Alviro, the previous version is still
    leaking @bank[n].

v2:
  - Fix wrong copy/paste.

## Summary
[PATCH v3 1/2] x86/delay: Fix the wrong asm constraint in `delay_loop()`

The asm constraint does not reflect that the asm statement can modify
the value of @loops. But the asm statement in delay_loop() does change
the @loops.

If by any chance the compiler inlines this function, it may clobber
random stuff (e.g. local variable, important temporary value in reg,
etc.).

Fortunately, delay_loop() is only called indirectly (so it can't
inline), and then the register it clobbers is %rax (which is by the
nature of the calling convention, it's a caller saved register), so it
didn't yield any bug.

^ That shouldn't be an excuse for using the wrong constraint anyway.

This changes "a" (as an input) to "+a" (as an input and output).


[PATCH v3 2/2] x86/mce/amd: Fix memory leak when `threshold_create_bank()` fails.

@bp is a local variable, calling mce_threshold_remove_device() when
threshold_create_bank() fails will not free the @bp. Note that
mce_threshold_remove_device() frees the @bp only if it's already
stored in the @threshold_banks per-CPU variable.

At that point, the @threshold_banks per-CPU variable is still NULL,
so the mce_threshold_remove_device() will just be a no-op and the
@bp is leaked.

Fix this by storing @bp to @threshold_banks before the loop, so in
case we fail, mce_threshold_remove_device() will free the @bp.

This bug is introduced by commit 6458de97fc15530b544 ("x86/mce/amd:
Straighten CPU hotplug path") [1].


Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Signed-off-by: Alviro Iskandar Setiawan <alviro.iskandar@gnuweeb.org>
Signed-off-by: Ammar Faizi <ammarfaizi2@gnuweeb.org>
---
Ammar Faizi (2):
  x86/delay: Fix the wrong asm constraint in `delay_loop()`
  x86/mce/amd: Fix memory leak when `threshold_create_bank()` fails

 arch/x86/kernel/cpu/mce/amd.c | 16 ++++++++++------
 arch/x86/lib/delay.c          |  4 ++--
 2 files changed, 12 insertions(+), 8 deletions(-)


base-commit: 7e57714cd0ad2d5bb90e50b5096a0e671dec1ef3