From: Tadeusz Struk <tadeusz.struk@linaro.org>
To: Theodore Ts'o <tytso@mit.edu>, Andreas Dilger <adilger.kernel@dilger.ca>
Cc: linux-ext4@vger.kernel.org
Subject: BUG in ext4_ind_remove_space
Date: Thu, 24 Feb 2022 17:12:56 -0800 [thread overview]
Message-ID: <48308b02-149b-1c47-115a-1a268dac6e24@linaro.org> (raw)
Hi,
Syzbot found an issue [1] in fallocate() that looks to me like a loss of precision.
The C reproducer [2] calls fallocate() and passes the size 0xffeffeff000ul, and
offset 0x1000000ul, which is then used to calculate the first_block and
stop_block using ext4_lblk_t type (u32). I think this gets the MSB of the size
truncated and leads to invalid calculations, and eventually his BUG() in
https://elixir.bootlin.com/linux/v5.16.11/source/fs/ext4/indirect.c#L1244
The issue can be reproduced on 5.17.0-rc5, but I don't think it's a new
regression. I spent some time debugging it, but could spot anything obvious.
Can someone have a look please.
[1] https://syzkaller.appspot.com/bug?id=b80bd9cf348aac724a4f4dff251800106d721331
[2] https://syzkaller.appspot.com/text?tag=ReproC&x=14ba0238700000
--
Thanks,
Tadeusz
next reply other threads:[~2022-02-25 1:13 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-25 1:12 Tadeusz Struk [this message]
2022-02-25 17:10 ` BUG in ext4_ind_remove_space Ritesh Harjani
2022-02-25 19:19 ` Tadeusz Struk
2022-03-02 23:14 ` Tadeusz Struk
2022-03-03 14:56 ` Ritesh Harjani
2022-03-03 15:37 ` Tadeusz Struk
2022-03-03 20:08 ` Ritesh Harjani
2022-03-07 5:45 ` Ritesh Harjani
2022-03-08 17:58 ` Tadeusz Struk
2022-03-14 21:27 ` Tadeusz Struk
2022-03-15 17:50 ` Tadeusz Struk
2022-03-15 19:15 ` [PATCH] ext4: check if offset+length is within a valid range in fallocate Tadeusz Struk
2022-03-15 20:39 ` Tadeusz Struk
2022-03-16 1:22 ` kernel test robot
2022-03-16 1:22 ` kernel test robot
2022-03-16 2:14 ` Tadeusz Struk
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