On Mon, May 6, 2024 at 8:48 PM Justin Stitt <justinstitt@xxxxxxxxxx> wrote:
>
Agh. Sorry about the noise, the first line of my patch body got eaten
by the subject line because a new line was missing in mutt.
FIXED in [v3] for real this time.
> [ 62.982337] ------------[ cut here ]------------
> [ 62.985692] cgroup: Invalid name
> [ 62.986211] UBSAN: signed-integer-overflow in ../block/ioctl.c:36:46
> [ 62.989370] 9pnet_fd: p9_fd_create_tcp (7343): problem connecting socket to 127.0.0.1
> [ 62.992992] 9223372036854775807 + 4095 cannot be represented in type 'long long'
> [ 62.997827] 9pnet_fd: p9_fd_create_tcp (7345): problem connecting socket to 127.0.0.1
> [ 62.999369] random: crng reseeded on system resumption
> [ 63.000634] GUP no longer grows the stack in syz-executor.2 (7353): 20002000-20003000 (20001000)
> [ 63.000668] CPU: 0 PID: 7353 Comm: syz-executor.2 Not tainted 6.8.0-rc2-00035-gb3ef86b5a957 #1
> [ 63.000677] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
> [ 63.000682] Call Trace:
> [ 63.000686] <TASK>
> [ 63.000731] dump_stack_lvl+0x93/0xd0
> [ 63.000919] __get_user_pages+0x903/0xd30
> [ 63.001030] __gup_longterm_locked+0x153e/0x1ba0
> [ 63.001041] ? _raw_read_unlock_irqrestore+0x17/0x50
> [ 63.001072] ? try_get_folio+0x29c/0x2d0
> [ 63.001083] internal_get_user_pages_fast+0x1119/0x1530
> [ 63.001109] iov_iter_extract_pages+0x23b/0x580
> [ 63.001206] bio_iov_iter_get_pages+0x4de/0x1220
> [ 63.001235] iomap_dio_bio_iter+0x9b6/0x1410
> [ 63.001297] __iomap_dio_rw+0xab4/0x1810
> [ 63.001316] iomap_dio_rw+0x45/0xa0
> [ 63.001328] ext4_file_write_iter+0xdde/0x1390
> [ 63.001372] vfs_write+0x599/0xbd0
> [ 63.001394] ksys_write+0xc8/0x190
> [ 63.001403] do_syscall_64+0xd4/0x1b0
> [ 63.001421] ? arch_exit_to_user_mode_prepare+0x3a/0x60
> [ 63.001479] entry_SYSCALL_64_after_hwframe+0x6f/0x77
> [ 63.001535] RIP: 0033:0x7f7fd3ebf539
> [ 63.001551] Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 14 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
> [ 63.001562] RSP: 002b:00007f7fd32570c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
> [ 63.001584] RAX: ffffffffffffffda RBX: 00007f7fd3ff3f80 RCX: 00007f7fd3ebf539
> [ 63.001590] RDX: 4db6d1e4f7e43360 RSI: 0000000020000000 RDI: 0000000000000004
> [ 63.001595] RBP: 00007f7fd3f1e496 R08: 0000000000000000 R09: 0000000000000000
> [ 63.001599] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> [ 63.001604] R13: 0000000000000006 R14: 00007f7fd3ff3f80 R15: 00007ffd415ad2b8
> ...
> [ 63.018142] ---[ end trace ]---
>
> 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 being re-enabled in the
> kernel with Commit 557f8c582a9ba8ab ("ubsan: Reintroduce signed overflow
> sanitizer").
>
> Let's rework this overflow checking logic to not actually perform an
> overflow during the check itself, thus avoiding the UBSAN splat.
>
> [1]: https://github.com/llvm/llvm-project/pull/82432
>
> Signed-off-by: Justin Stitt <justinstitt@xxxxxxxxxx>
> ---
> Changes in v2:
> - don't use check_add_overflow as I accidentally was writing to p.start
> and the alternative of using a dummy (unused) variable does not seem great.
> - Link to v1: https://lore.kernel.org/r/20240506-b4-sio-block-ioctl-v1-1-da535cc020dc@xxxxxxxxxx
> ---
> block/ioctl.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/block/ioctl.c b/block/ioctl.c
> index f505f9c341eb..2639ce9df385 100644
> --- a/block/ioctl.c
> +++ b/block/ioctl.c
> @@ -33,7 +33,7 @@ static int blkpg_do_ioctl(struct block_device *bdev,
> if (op == BLKPG_DEL_PARTITION)
> return bdev_del_partition(disk, p.pno);
>
> - if (p.start < 0 || p.length <= 0 || p.start + p.length < 0)
> + if (p.start < 0 || p.length <= 0 || LLONG_MAX - p.length < p.start)
> return -EINVAL;
> /* Check that the partition is aligned to the block size */
> if (!IS_ALIGNED(p.start | p.length, bdev_logical_block_size(bdev)))
>
> ---
> base-commit: 0106679839f7c69632b3b9833c3268c316c0a9fc
> change-id: 20240506-b4-sio-block-ioctl-78efd742fff4
>
> Best regards,
> --
> Justin Stitt <justinstitt@xxxxxxxxxx>
>
[v3]: https://lore.kernel.org/all/20240507-b4-sio-block-ioctl-v3-1-ba0c2b32275e@xxxxxxxxxx/
Thanks
Justin
