From: Al Viro <viro@zeniv.linux.org.uk>
To: Hao Ge <gehao@kylinos.cn>
Cc: brauner@kernel.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org, gehao618@163.com
Subject: Re: [PATCH V2] fs: fix undefined behavior in bit shift for SB_NOUSER
Date: Mon, 24 Apr 2023 06:01:58 +0100 [thread overview]
Message-ID: <20230424050158.GN3390869@ZenIV> (raw)
In-Reply-To: <20230424045122.370511-1-gehao@kylinos.cn>
On Mon, Apr 24, 2023 at 12:51:22PM +0800, Hao Ge wrote:
> Shifting signed 32-bit value by 31 bits is undefined, so changing
> significant bit to unsigned. The UBSAN warning calltrace like below:
> UBSAN: shift-out-of-bounds in fs/nsfs.c:306:32
> left shift of 1 by 31 places cannot be represented in type 'int'
> CPU: 0 PID: 0 Comm: swapper/0 Not tainted 6.3.0-rc4+ #2
> Call trace:
> <TASK>
> dump_backtrace+0x134/0x1e0
> show_stack+0x2c/0x3c
> dump_stack_lvl+0xb0/0xd4
> dump_stack+0x14/0x1c
> ubsan_epilogue+0xc/0x3c
> __ubsan_handle_shift_out_of_bounds+0xb0/0x14c
> nsfs_init+0x4c/0xb0
> start_kernel+0x38c/0x738
> __primary_switched+0xbc/0xc4
> </TASK>
>
> Fixes: e462ec50cb5f ("VFS: Differentiate mount flags (MS_*) from internal superblock flags")
> Signed-off-by: Hao Ge <gehao@kylinos.cn>
*snort*
IMO something like "spotted by UBSAN" is more than enough here -
stack trace is completely pointless.
Otherwise, no problems with the patch - it's obviously safe.
next prev parent reply other threads:[~2023-04-24 5:02 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-24 3:00 [PATCH] fs: fix undefined behavior in bit shift for SB_NOUSER Hao Ge
2023-04-24 4:51 ` [PATCH V2] " Hao Ge
2023-04-24 5:01 ` Al Viro [this message]
2023-04-24 5:18 ` [PATCH V3] " Hao Ge
2023-04-24 5:43 ` [PATCH V2] " Hao Ge
-- strict thread matches above, loose matches on Subject: below --
2022-10-31 13:48 [PATCH v2] " Gaosheng Cui
2022-10-31 13:50 ` Christoph Hellwig
2022-10-31 13:53 ` Matthew Wilcox
2022-10-31 14:05 ` Christoph Hellwig
2022-10-31 14:36 ` cuigaosheng
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