From: Justin Stitt <justinstitt@google.com>
To: Phillip Potter <phil@philpotter.co.uk>,
Nathan Chancellor <nathan@kernel.org>,
Bill Wendling <morbo@google.com>
Cc: linux-kernel@vger.kernel.org, llvm@lists.linux.dev,
linux-hardening@vger.kernel.org,
Justin Stitt <justinstitt@google.com>
Subject: [PATCH] cdrom: rearrange last_media_change check to avoid unintentional overflow
Date: Tue, 07 May 2024 04:54:04 +0000 [thread overview]
Message-ID: <20240507-b4-sio-ata1-v1-1-810ffac6080a@google.com> (raw)
When running syzkaller with the newly reintroduced signed integer wrap
sanitizer we encounter this splat:
[ 366.015950] UBSAN: signed-integer-overflow in ../drivers/cdrom/cdrom.c:2361:33
[ 366.021089] -9223372036854775808 - 346321 cannot be represented in type '__s64' (aka 'long long')
[ 366.025894] program syz-executor.4 is using a deprecated SCSI ioctl, please convert it to SG_IO
[ 366.027502] CPU: 5 PID: 28472 Comm: syz-executor.7 Not tainted 6.8.0-rc2-00035-gb3ef86b5a957 #1
[ 366.027512] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
[ 366.027518] Call Trace:
[ 366.027523] <TASK>
[ 366.027533] dump_stack_lvl+0x93/0xd0
[ 366.027899] handle_overflow+0x171/0x1b0
[ 366.038787] ata1.00: invalid multi_count 32 ignored
[ 366.043924] cdrom_ioctl+0x2c3f/0x2d10
[ 366.063932] ? __pm_runtime_resume+0xe6/0x130
[ 366.071923] sr_block_ioctl+0x15d/0x1d0
[ 366.074624] ? __pfx_sr_block_ioctl+0x10/0x10
[ 366.077642] blkdev_ioctl+0x419/0x500
[ 366.080231] ? __pfx_blkdev_ioctl+0x10/0x10
...
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 rearrange the check to not perform any arithmetic, thus not
tripping the sanitizer.
Link: https://github.com/llvm/llvm-project/pull/82432 [1]
Closes: https://github.com/KSPP/linux/issues/354
Cc: linux-hardening@vger.kernel.org
Signed-off-by: Justin Stitt <justinstitt@google.com>
---
drivers/cdrom/cdrom.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/cdrom/cdrom.c b/drivers/cdrom/cdrom.c
index a5e07270e0d4..20c90ebb3a3f 100644
--- a/drivers/cdrom/cdrom.c
+++ b/drivers/cdrom/cdrom.c
@@ -2358,7 +2358,7 @@ static int cdrom_ioctl_timed_media_change(struct cdrom_device_info *cdi,
return -EFAULT;
tmp_info.media_flags = 0;
- if (tmp_info.last_media_change - cdi->last_media_change_ms < 0)
+ if (cdi->last_media_change_ms > tmp_info.last_media_change)
tmp_info.media_flags |= MEDIA_CHANGED_FLAG;
tmp_info.last_media_change = cdi->last_media_change_ms;
---
base-commit: 0106679839f7c69632b3b9833c3268c316c0a9fc
change-id: 20240507-b4-sio-ata1-9d64089f91c0
Best regards,
--
Justin Stitt <justinstitt@google.com>
next reply other threads:[~2024-05-07 4:54 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-07 4:54 Justin Stitt [this message]
2024-05-07 20:53 ` [PATCH] cdrom: rearrange last_media_change check to avoid unintentional overflow Phillip Potter
2024-05-08 0:09 ` Kees Cook
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