[syzbot] [media?] [usb?] KASAN: slab-out-of-bounds Read in ec168_i2c_xfer

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 785f0eb2f85d Add linux-next specific files for 20260320
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=12cc5e02580000
kernel config: https://syzkaller.appspot.com/x/.config?x=c584910d0d74158d
dashboard link: https://syzkaller.appspot.com/bug?extid=64485d3659c4c07111b4
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1689e06a580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12e22cba580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/a1f7fd9c1a63/disk-785f0eb2.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6c138da87c25/vmlinux-785f0eb2.xz
kernel image: https://storage.googleapis.com/syzbot-assets/4d1be64e56db/bzImage-785f0eb2.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+64485d...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-out-of-bounds in ec168_i2c_xfer+0x4cd/0x640 drivers/media/usb/dvb-usb-v2/ec168.c:143
Read of size 1 at addr ffff888022a8e061 by task syz.0.17/6065

CPU: 0 UID: 0 PID: 6065 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
<TASK>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_address_description+0x55/0x1e0 mm/kasan/report.c:378
print_report+0x58/0x70 mm/kasan/report.c:482
kasan_report+0x117/0x150 mm/kasan/report.c:595
ec168_i2c_xfer+0x4cd/0x640 drivers/media/usb/dvb-usb-v2/ec168.c:143
__i2c_transfer+0x79a/0x1f70 drivers/i2c/i2c-core-base.c:-1
i2c_transfer+0x1cc/0x2d0 drivers/i2c/i2c-core-base.c:2317
i2cdev_ioctl_rdwr+0x460/0x740 drivers/i2c/i2c-dev.c:306
i2cdev_ioctl+0x6a5/0x880 drivers/i2c/i2c-dev.c:467
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:597 [inline]
__se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc935d9c799
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffef6f8b6b8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fc936015fa0 RCX: 00007fc935d9c799
RDX: 0000200000000140 RSI: 0000000000000707 RDI: 0000000000000004
RBP: 00007fc935e32c99 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc936015fac R14: 00007fc936015fa0 R15: 00007fc936015fa0
</TASK>

Allocated by task 6065:
kasan_save_stack mm/kasan/common.c:57 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
__kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:415
kasan_kmalloc include/linux/kasan.h:263 [inline]
__do_kmalloc_node mm/slub.c:5292 [inline]
__kmalloc_node_track_caller_noprof+0x4db/0x7b0 mm/slub.c:5400
memdup_user+0x2b/0xd0 mm/util.c:221
i2cdev_ioctl_rdwr+0x1c6/0x740 drivers/i2c/i2c-dev.c:266
i2cdev_ioctl+0x6a5/0x880 drivers/i2c/i2c-dev.c:467
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:597 [inline]
__se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff888022a8e060
which belongs to the cache kmalloc-8 of size 8
The buggy address is located 0 bytes to the right of
allocated 1-byte region [ffff888022a8e060, ffff888022a8e061)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff888022a8e260 pfn:0x22a8e
flags: 0xfff00000000200(workingset|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000200 ffff88801b041500 ffffea0000a17150 ffffea0000cd6d90
raw: ffff888022a8e260 000000080080007b 00000000f5000000 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0xd2cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, tgid 1 (swapper/0), ts 3746368734, free_ts 0
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x231/0x280 mm/page_alloc.c:1859
prep_new_page mm/page_alloc.c:1867 [inline]
get_page_from_freelist+0x2418/0x24b0 mm/page_alloc.c:3926
__alloc_frozen_pages_noprof+0x233/0x3d0 mm/page_alloc.c:5213
alloc_slab_page mm/slub.c:3278 [inline]
allocate_slab+0x77/0x660 mm/slub.c:3467
new_slab mm/slub.c:3525 [inline]
refill_objects+0x339/0x3d0 mm/slub.c:7247
refill_sheaf mm/slub.c:2816 [inline]
__pcs_replace_empty_main+0x321/0x720 mm/slub.c:4651
alloc_from_pcs mm/slub.c:4749 [inline]
slab_alloc_node mm/slub.c:4883 [inline]
__do_kmalloc_node mm/slub.c:5291 [inline]
__kmalloc_noprof+0x474/0x760 mm/slub.c:5304
kmalloc_noprof include/linux/slab.h:954 [inline]
kzalloc_noprof include/linux/slab.h:1188 [inline]
acpi_ns_internalize_name+0x2c9/0x3e0 drivers/acpi/acpica/nsutils.c:331
acpi_ns_get_node_unlocked+0x186/0x480 drivers/acpi/acpica/nsutils.c:666
acpi_ns_get_node+0x76/0xc0 drivers/acpi/acpica/nsutils.c:726
acpi_ns_evaluate+0x283/0x1230 drivers/acpi/acpica/nseval.c:62
acpi_evaluate_object+0x657/0xd50 drivers/acpi/acpica/nsxfeval.c:354
acpi_evaluate_dsm drivers/acpi/utils.c:797 [inline]
acpi_check_dsm+0x1bb/0x6f0 drivers/acpi/utils.c:830
device_has_acpi_name drivers/pci/pci-label.c:44 [inline]
acpi_attr_is_visible+0x89/0xe0 drivers/pci/pci-label.c:221
create_files fs/sysfs/group.c:69 [inline]
internal_create_group+0x5e5/0x1180 fs/sysfs/group.c:189
internal_create_groups fs/sysfs/group.c:229 [inline]
sysfs_create_groups+0x59/0x120 fs/sysfs/group.c:255
page_owner free stack trace missing

Memory state around the buggy address:
ffff888022a8df00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888022a8df80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888022a8e000: fa fc fc fc fa fc fc fc fa fc fc fc 01 fc fc fc
^
ffff888022a8e080: 00 fc fc fc fa fc fc fc fa fc fc fc 07 fc fc fc
ffff888022a8e100: 07 fc fc fc 05 fc fc fc fa fc fc fc 06 fc fc fc
==================================================================


---
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[syzbot]

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***

Subject: [PATCH] media: ec168: fix slab-out-of-bounds in ec168_i2c_xfer
Author: karti...@gmail.com

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master


The WRITE_DEMOD path in ec168_i2c_xfer() checks msg[i].len < 1
before accessing the buffer, but then reads both buf[0] (register)
and buf[1] (value). If userspace supplies a 1-byte I2C message,
the read of buf[1] goes out of bounds, triggering a KASAN
slab-out-of-bounds error.

Fix by requiring msg[i].len >= 2 in the WRITE_DEMOD path before
accessing the buffer.

Fixes: a6dcefcc08ec ("media: dvb-usb-v2: ec168: fix null-ptr-deref in ec168_i2c_xfer()")
Reported-by: syzbot+64485d...@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=64485d3659c4c07111b4
Signed-off-by: Deepanshu Kartikey <Karti...@gmail.com>
---
drivers/media/usb/dvb-usb-v2/ec168.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/media/usb/dvb-usb-v2/ec168.c b/drivers/media/usb/dvb-usb-v2/ec168.c
index 973b32356b17..ebfb02826b20 100644
--- a/drivers/media/usb/dvb-usb-v2/ec168.c
+++ b/drivers/media/usb/dvb-usb-v2/ec168.c
@@ -135,7 +135,7 @@ static int ec168_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msg[],
}
} else {
if (msg[i].addr == ec168_ec100_config.demod_address) {
- if (msg[i].len < 1) {
+ if (msg[i].len < 2) {
i = -EOPNOTSUPP;
break;
}
--
2.43.0

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+64485d...@syzkaller.appspotmail.com
Tested-by: syzbot+64485d...@syzkaller.appspotmail.com

Tested on:

commit: 09c0f7f1 Add linux-next specific files for 20260323
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1311c1d6580000
kernel config: https://syzkaller.appspot.com/x/.config?x=c0c30527ccbcb0f2

dashboard link: https://syzkaller.appspot.com/bug?extid=64485d3659c4c07111b4
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

patch: https://syzkaller.appspot.com/x/patch.diff?x=1676aa06580000

Note: testing is done by a robot and is best-effort only.