Re: [PATCH 4/4] mm/madvise: remove redundant mmap_lock operations from process_madvise()

[SeongJae Park]

Hello Lai,

On Tue, 11 Feb 2025 13:30:49 +0800 "Lai, Yi" <yi1.lai@xxxxxxxxxxxxxxx> wrote:

[...]
> Hi SeongJae Park,
> 
> Greetings!
> 
> I used Syzkaller and found that there is WARNING in madvise_unlock in linux-next tag - next-20250210.

Thank you so much for this nice report!  I just sent a fix:
https://lore.kernel.org/20250211063201.5106-1-sj@xxxxxxxxxx

> 
> After bisection and the first bad commit is:
> "
> ec68fbd9e99f mm/madvise: remove redundant mmap_lock operations from process_madvise()
> "

Nonetheless, I think the real first bad commit is f19c9d7b57cf ("mm/madvise:
split out madvise() behavior execution").  I confirmed I can reproduce the
issue using your reproducer on the commit.  And I think the fix may better to
be squashed into an earlier commit, 948a0a9ea070 ("mm/madvise: split out mmap
locking operations for madvise()").  Please refer to the fix for details about
why I think so, and let me know if anything seems wrong.


Thanks,
SJ

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