From: Kees Cook <keescook@chromium.org>
To: Justin Stitt <justinstitt@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>,
Christian Brauner <brauner@kernel.org>, Jan Kara <jack@suse.cz>,
Nathan Chancellor <nathan@kernel.org>,
Bill Wendling <morbo@google.com>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
llvm@lists.linux.dev, linux-hardening@vger.kernel.org
Subject: Re: [PATCH] fs: remove accidental overflow during wraparound check
Date: Tue, 7 May 2024 17:11:14 -0700 [thread overview]
Message-ID: <202405071710.1B6F1990@keescook> (raw)
In-Reply-To: <20240507-b4-sio-vfs_fallocate-v1-1-322f84b97ad5@google.com>
On Tue, May 07, 2024 at 11:17:57PM +0000, Justin Stitt wrote:
> Running syzkaller with the newly enabled signed integer overflow
> sanitizer produces this report:
>
> [ 195.401651] ------------[ cut here ]------------
> [ 195.404808] UBSAN: signed-integer-overflow in ../fs/open.c:321:15
> [ 195.408739] 9223372036854775807 + 562984447377399 cannot be represented in type 'loff_t' (aka 'long long')
> [ 195.414683] CPU: 1 PID: 703 Comm: syz-executor.0 Not tainted 6.8.0-rc2-00039-g14de58dbe653-dirty #11
> [ 195.420138] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
> [ 195.425804] Call Trace:
> [ 195.427360] <TASK>
> [ 195.428791] dump_stack_lvl+0x93/0xd0
> [ 195.431150] handle_overflow+0x171/0x1b0
> [ 195.433640] vfs_fallocate+0x459/0x4f0
> ...
> [ 195.490053] ------------[ cut here ]------------
> [ 195.493146] UBSAN: signed-integer-overflow in ../fs/open.c:321:61
> [ 195.497030] 9223372036854775807 + 562984447377399 cannot be represented in type 'loff_t' (aka 'long long)
> [ 195.502940] CPU: 1 PID: 703 Comm: syz-executor.0 Not tainted 6.8.0-rc2-00039-g14de58dbe653-dirty #11
> [ 195.508395] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
> [ 195.514075] Call Trace:
> [ 195.515636] <TASK>
> [ 195.517000] dump_stack_lvl+0x93/0xd0
> [ 195.519255] handle_overflow+0x171/0x1b0
> [ 195.521677] vfs_fallocate+0x4cb/0x4f0
> [ 195.524033] __x64_sys_fallocate+0xb2/0xf0
>
> Historically, the signed integer overflow sanitizer did not work in the
> kernel due to its interaction with `-fwrapv` but this has since been
> changed [1] in the newest version of Clang. It was re-enabled in the
> kernel with Commit 557f8c582a9ba8ab ("ubsan: Reintroduce signed overflow
> sanitizer").
>
> Let's use the check_add_overflow helper to first verify the addition
> stays within the bounds of its type (long long); then we can use that
> sum for the following check.
>
> Link: https://github.com/llvm/llvm-project/pull/82432 [1]
> Closes: https://github.com/KSPP/linux/issues/356
> Cc: linux-hardening@vger.kernel.org
> Signed-off-by: Justin Stitt <justinstitt@google.com>
I think this makes the checking more reading too. Thanks
Reviewed-by: Kees Cook <keescook@chromium.org>
--
Kees Cook
next prev parent reply other threads:[~2024-05-08 0:11 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-07 23:17 [PATCH] fs: remove accidental overflow during wraparound check Justin Stitt
2024-05-08 0:10 ` Al Viro
2024-05-08 0:11 ` Kees Cook [this message]
2024-05-09 15:53 ` Jan Kara
2024-05-09 22:10 ` Justin Stitt
2024-05-12 8:05 ` Jan Kara
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