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References: <CGME20240531101615epcas1p3f0085b563af62c7f83699b0135cc832a@epcas1p3.samsung.com>
 <20240531101444.1874926-1-sj1557.seo@samsung.com>
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From: Namjae Jeon <linkinjeon@kernel.org>
Date: Mon, 3 Jun 2024 20:50:29 +0900
Message-ID: <CAKYAXd8UD7bzUJ4wntiSMEn+x=anoaJcfisKJoNSUo67F_HpjA@mail.gmail.com>
Subject: Re: [PATCH] exfat: fix potential deadlock on __exfat_get_dentry_set
To: Sungjong Seo <sj1557.seo@samsung.com>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, 
	stable@vger.kernel.org, syzbot+412a392a2cd4a65e71db@syzkaller.appspotmail.com
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2024=EB=85=84 5=EC=9B=94 31=EC=9D=BC (=EA=B8=88) =EC=98=A4=ED=9B=84 7:16, S=
ungjong Seo <sj1557.seo@samsung.com>=EB=8B=98=EC=9D=B4 =EC=9E=91=EC=84=B1:
>
> When accessing a file with more entries than ES_MAX_ENTRY_NUM, the bh-arr=
ay
> is allocated in __exfat_get_entry_set. The problem is that the bh-array i=
s
> allocated with GFP_KERNEL. It does not make sense. In the following cases=
,
> a deadlock for sbi->s_lock between the two processes may occur.
>
>        CPU0                CPU1
>        ----                ----
>   kswapd
>    balance_pgdat
>     lock(fs_reclaim)
>                       exfat_iterate
>                        lock(&sbi->s_lock)
>                        exfat_readdir
>                         exfat_get_uniname_from_ext_entry
>                          exfat_get_dentry_set
>                           __exfat_get_dentry_set
>                            kmalloc_array
>                             ...
>                             lock(fs_reclaim)
>     ...
>     evict
>      exfat_evict_inode
>       lock(&sbi->s_lock)
>
> To fix this, let's allocate bh-array with GFP_NOFS.
>
> Fixes: a3ff29a95fde ("exfat: support dynamic allocate bh for exfat_entry_=
set_cache")
> Cc: stable@vger.kernel.org # v6.2+
> Reported-by: syzbot+412a392a2cd4a65e71db@syzkaller.appspotmail.com
> Closes: https://lore.kernel.org/lkml/000000000000fef47e0618c0327f@google.=
com
> Signed-off-by: Sungjong Seo <sj1557.seo@samsung.com>
Applied it to #dev.
Thanks for your patch!