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From: "Yosry Ahmed" Message-ID: <3482501981b13aedda3c1c6b54d83d496bd05922@linux.dev> TLS-Required: No Subject: Re: mm: zswap: fix crypto_free_acomp deadlock in zswap_cpu_comp_dead To: "Herbert Xu" , "syzbot" Cc: davem@davemloft.net, linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, "Andrew Morton" , linux-mm@kvack.org In-Reply-To: References: <67bcea51.050a0220.bbfd1.0096.GAE@google.com> X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Stat-Signature: wcbunxrizdz96jxtfbpx1c4dau9e6jd7 X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 456CD20008 X-HE-Tag: 1740491026-53794 X-HE-Meta: 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 pEa35Y1u uX3kkrIGymqNty6yt90udW6kl1KWhTMXaiRIZUrKOSfOhzY6D7jh46xCqdoSsgSyUaPcdgAjfCLL5MIY/u9qMHXclMH6A2fF9vviLZgtp3LkNFr6H/HXli3y11ZY+Bum/NYPQOjJZ9xpD+Z9NpDMQnLrzAXjd5oJ3F+Juy13Kv0qz+vKl1dGCzDbd1C1NjeUxoGgeAg1B//plulxJFt3qXkCyj6K3Ett09cYGO9E9g0/i9oE8JnWpjSXcnDhb7Vt+H6vhio+KBlj/GdQVAaYP+ju1nXT1MvviOzPIu4YQoxBjaW0O18f7LmKe+jJxhwd2kYcepH3T+L0w0m+oDJOZkBN7SiKL26QKeuO+BzV3Vsmy7w6hoL/0qjlj20A8ky0buHtPapCdRAOIy1O9xt9jkFC+GkVtusDTEDjqjR6Z1Zkk7zhbalG3k4BQbGtT3i0CIKzvYXOOVvg5ANdi3h2U/nWI0fg2b30u5t8KzKFoOZtMjGRjQvrMqzJN/mxM72jw+c/9LtSQHiP4AylISWTBmzaLe/r/zVd6cXAIDjF0te6Gj4d4cuaKKEBPbDAj28HKIpdb86DQt+VV+IC8YY+HT4agEk6facA3TC/m3l6zTaJCpnO8ZdOy1U+tVq8Xm5V4xfkAfgMncSPRpNM/JXFv25aCkiRxl2sndI33XlVkE0Q9bSjZO8CBGC0Iqr8HkyDeRGi6+sS+rLPEHmQcZqVMZZiEkhguyUdJCqY7bLu1o1ogR/lDRe70/pJ9MQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: February 25, 2025 at 12:53 AM, "Herbert Xu" = wrote: >=20 >=20On Mon, Feb 24, 2025 at 01:53:21PM -0800, syzbot wrote: >=20 >=20> syzbot found the following issue on: > >=20 >=20> HEAD commit: e9a8cac0bf89 Merge tag 'v6.14-rc3-smb3-client-fixes' = of gi.. > > git tree: upstream > > console output: https://syzkaller.appspot.com/x/log.txt?x=3D17b667f8= 580000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=3D61cbf5ac8= a063ad4 > > dashboard link: https://syzkaller.appspot.com/bug?extid=3D1a517ccfcb= c6a7ab0f82 > >=20 >=20> compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for = Debian) 2.40=20 >=20>=20 >=20> Unfortunately, I don't have any reproducer for this issue yet. > >=20=20 >=20> Downloadable assets: > > disk image: https://storage.googleapis.com/syzbot-assets/8441f1b5040= 2/disk-e9a8cac0.raw.xz > > vmlinux: https://storage.googleapis.com/syzbot-assets/65b1f8d2f790/v= mlinux-e9a8cac0.xz=20 >=20> kernel image: https://storage.googleapis.com/syzbot-assets/1d6f6d8= c3d6b/bzImage-e9a8cac0.xz > >=20 >=20 > ---8<--- >=20 >=20Call crypto_free_acomp outside of the mutex in zswap_cpu_comp_dead > as otherwise this could dead-lock as the allocation path may lead > back into zswap while holding the same lock. Zap the pointers to > acomp and buffer after freeing. > Also move the NULL check on acomp_ctx so that it takes place before > the mutex dereference. >=20 >=20Fixes: 12dcb0ef5406 ("mm: zswap: properly synchronize freeing resourc= es during CPU hotunplug") > Reported-by: syzbot+1a517ccfcbc6a7ab0f82@syzkaller.appspotmail.com > Signed-off-by: Herbert Xu Interesting, it's weird that crypto_free_acomp() allocates memory. Do you= have the specific call path?