[syzbot] [greybus?] [usb?] KASAN: slab-out-of-bounds Read in gb_operation_work

[syzbot] [greybus?] [usb?] KASAN: slab-out-of-bounds Read in gb_operation_work

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    6628e7d4c6b2 Linux 7.4-rc1
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing
console output: https://syzkaller.appspot.com/x/log.txt?x=109ac1a1580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f9bf69220d319004
dashboard link: https://syzkaller.appspot.com/bug?extid=0b456664585fa81a47f6
compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=149ac1a1580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=150c9f8d580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/d415be35d54e/disk-6628e7d4.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/69e49385122b/vmlinux-6628e7d4.xz
kernel image: https://storage.googleapis.com/syzbot-assets/51be81fff25f/bzImage-6628e7d4.xz

AI-generated root cause summary:
In gb_connection_recv() (drivers/greybus/operation.c), the kernel verifies that
the incoming buffer length is at least sizeof(struct gb_operation_msg_hdr), but
fails to validate that the message header's claimed size (header.size, parsed as
msg_size) is also at least sizeof(struct gb_operation_msg_hdr). When msg_size <
sizeof(struct gb_operation_msg_hdr), gb_operation_create_incoming() subtracts
the header size from msg_size, causing an unsigned integer underflow when
calculating request_size. In gb_operation_message_alloc(), the payload size and
header size wrap back around and kzalloc(msg_size) allocates an undersized
buffer smaller than the header, leading to out-of-bounds reads when reading
request_header->operation_id or a ZERO_SIZE_PTR dereference panic when msg_size
is zero.

full analysis:  https://syzkaller.appspot.com/x/ai_root_cause?x=0b456664585fa81a47f6

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+0b456664585fa81a47f6@syzkaller.appspotmail.com

greybus 1-svc: unexpected request 0x7f received (state 0)
==================================================================
BUG: KASAN: slab-out-of-bounds in gb_operation_response_alloc drivers/greybus/operation.c:490 [inline]
BUG: KASAN: slab-out-of-bounds in gb_operation_response_send drivers/greybus/operation.c:832 [inline]
BUG: KASAN: slab-out-of-bounds in gb_operation_request_handle drivers/greybus/operation.c:252 [inline]
BUG: KASAN: slab-out-of-bounds in gb_operation_work+0x8be/0x990 drivers/greybus/operation.c:280
Read of size 2 at addr ffff888105f0a642 by task kworker/u8:2/38

CPU: 1 UID: 0 PID: 38 Comm: kworker/u8:2 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/15/2026
Workqueue: greybus1:0 gb_operation_work
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0x13d/0x4b0 mm/kasan/report.c:482
 kasan_report+0xdf/0x1c0 mm/kasan/report.c:595
 gb_operation_response_alloc drivers/greybus/operation.c:490 [inline]
 gb_operation_response_send drivers/greybus/operation.c:832 [inline]
 gb_operation_request_handle drivers/greybus/operation.c:252 [inline]
 gb_operation_work+0x8be/0x990 drivers/greybus/operation.c:280
 process_one_work+0xac7/0x1b10 kernel/workqueue.c:3495
 process_scheduled_works kernel/workqueue.c:3578 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3659
 kthread+0x373/0x450 kernel/kthread.c:436
 ret_from_fork+0x69f/0xc90 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Allocated by task 28:
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_save_track+0x14/0x30 mm/kasan/common.c:78
 poison_kmalloc_redzone mm/kasan/common.c:409 [inline]
 __kasan_kmalloc+0x8f/0xa0 mm/kasan/common.c:426
 kasan_kmalloc include/linux/kasan.h:263 [inline]
 __do_kmalloc_node mm/slub.c:5531 [inline]
 __kmalloc_noprof+0x315/0x7e0 mm/slub.c:5556
 _kmalloc_noprof include/linux/slab.h:995 [inline]
 _kzalloc_noprof include/linux/slab.h:1312 [inline]
 gb_operation_message_alloc+0x9b/0x2c0 drivers/greybus/operation.c:380
 gb_operation_create_common+0x9f/0x710 drivers/greybus/operation.c:532
 gb_operation_create_incoming drivers/greybus/operation.c:644 [inline]
 gb_connection_recv_request drivers/greybus/operation.c:926 [inline]
 gb_connection_recv+0x1dc/0x1050 drivers/greybus/operation.c:1063
 greybus_data_rcvd+0x244/0x600 drivers/greybus/connection.c:89
 cport_in_callback+0x1fb/0x280 drivers/greybus/es2.c:840
 __usb_hcd_giveback_urb+0x38e/0x610 drivers/usb/core/hcd.c:1657
 usb_hcd_giveback_urb+0x3ca/0x4a0 drivers/usb/core/hcd.c:1741
 dummy_timer+0xdb5/0x3840 drivers/usb/gadget/udc/dummy_hcd.c:2051
 __run_hrtimer kernel/time/hrtimer.c:2079 [inline]
 __hrtimer_run_queues+0x448/0x9a0 kernel/time/hrtimer.c:2136
 hrtimer_run_softirq+0x1ca/0x360 kernel/time/hrtimer.c:2153
 handle_softirqs+0x209/0xa00 kernel/softirq.c:669
 __do_softirq kernel/softirq.c:703 [inline]
 invoke_softirq kernel/softirq.c:542 [inline]
 __irq_exit_rcu+0x17a/0x220 kernel/softirq.c:786
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:809
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
 sysvec_apic_timer_interrupt+0x8f/0xb0 arch/x86/kernel/apic/apic.c:1062
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674

The buggy address belongs to the object at ffff888105f0a640
 which belongs to the cache kmalloc-8 of size 8
The buggy address is located 2 bytes inside of
 allocated 3-byte region [ffff888105f0a640, ffff888105f0a643)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x105f0a
flags: 0x200000000000000(node=0|zone=2)
page_type: f5(slab)
raw: 0200000000000000 ffff888100041500 dead000000000100 dead000000000122
raw: 0000000000000000 0000000000800080 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 0xd2c00(GFP_NOIO|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, tgid 1 (swapper/0), ts 6490716744
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0xfd/0x120 mm/page_alloc.c:1856
 prep_new_page mm/page_alloc.c:1864 [inline]
 get_page_from_freelist+0xf4b/0x3440 mm/page_alloc.c:3935
 __alloc_frozen_pages_noprof+0x299/0x2d50 mm/page_alloc.c:5444
 alloc_slab_page mm/slub.c:3384 [inline]
 allocate_slab mm/slub.c:3499 [inline]
 new_slab+0xb1/0x6d0 mm/slub.c:3550
 refill_objects+0xe3/0x410 mm/slub.c:7539
 refill_sheaf mm/slub.c:2917 [inline]
 __pcs_replace_empty_main+0x35e/0x650 mm/slub.c:4811
 alloc_from_pcs mm/slub.c:4887 [inline]
 slab_alloc_node mm/slub.c:5021 [inline]
 __do_kmalloc_node mm/slub.c:5530 [inline]
 __kmalloc_node_noprof+0x634/0x820 mm/slub.c:5543
 _kmalloc_array_node_noprof include/linux/slab.h:1297 [inline]
 __blk_mq_realloc_hw_ctxs+0x579/0x820 block/blk-mq.c:4588
 blk_mq_realloc_hw_ctxs block/blk-mq.c:4652 [inline]
 blk_mq_init_allocated_queue+0x36c/0x1500 block/blk-mq.c:4694
 blk_mq_alloc_queue+0x1bd/0x290 block/blk-mq.c:4464
 scsi_alloc_sdev+0x972/0xe90 drivers/scsi/scsi_scan.c:339
 scsi_probe_and_add_lun+0x523/0x720 drivers/scsi/scsi_scan.c:1227
 __scsi_scan_target+0x188/0x420 drivers/scsi/scsi_scan.c:1803
 scsi_scan_channel drivers/scsi/scsi_scan.c:1893 [inline]
 scsi_scan_channel+0x142/0x1e0 drivers/scsi/scsi_scan.c:1868
 scsi_scan_host_selected+0x2b3/0x380 drivers/scsi/scsi_scan.c:1922
 do_scsi_scan_host+0x1f4/0x270 drivers/scsi/scsi_scan.c:2055
page_owner free stack trace missing

Memory state around the buggy address:
 ffff888105f0a500: 06 fc fc fc 00 fc fc fc 00 fc fc fc 00 fc fc fc
 ffff888105f0a580: fa fc fc fc 06 fc fc fc 06 fc fc fc 06 fc fc fc
>ffff888105f0a600: 06 fc fc fc 00 fc fc fc 03 fc fc fc fa fc fc fc
                                           ^
 ffff888105f0a680: fa fc fc fc 00 fc fc fc fa fc fc fc 00 fc fc fc
 ffff888105f0a700: fa fc fc fc 05 fc fc fc 05 fc fc fc 05 fc fc fc
==================================================================


---
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[PATCH] greybus: verify the received message size covers the message header

[Shunbo Shi]

In gb_connection_recv(), the size of the received data is checked
against sizeof(struct gb_operation_msg_hdr) and against the message
size encoded in the header (msg_size), but msg_size itself is never
checked against the header size.

If a peer sends a message whose header claims a size smaller than
the header itself (e.g. header.size == 3), the two existing checks
both pass (size >= sizeof(header) and size >= msg_size), and the
message is dispatched with the undersized msg_size.

In gb_operation_create_incoming(), this leads to an unsigned
integer underflow in:

	request_size = size - sizeof(struct gb_operation_msg_hdr);

The underflowed request_size then wraps back around in
gb_operation_message_alloc():

	message_size = payload_size + sizeof(*header);

causing kzalloc() to allocate a buffer that is too small to hold
the message header.  When the response is later prepared in
gb_operation_response_alloc(), reading
request_header->operation_id reads past the end of the undersized
allocation, triggering a KASAN slab-out-of-bounds report.  When
header.size is zero, kzalloc(0) returns ZERO_SIZE_PTR and the
same read dereferences an invalid address.

Verify msg_size >= sizeof(header) in gb_connection_recv() so that
the "Caller has made sure we at least have a message header"
assumption in gb_operation_create_incoming() actually holds.

Fixes: d90c25b0a279 ("greybus: let operation layer examine incoming data")
Reported-by: syzbot+0b456664585fa81a47f6@syzkaller.appspotmail.com
Closes: https://syzbot.org/bug?extid=0b456664585fa81a47f6
Signed-off-by: Shunbo Shi <shishunbo@cmss.chinamobile.com>
---
 drivers/greybus/operation.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/greybus/operation.c b/drivers/greybus/operation.c
index 7e12ffb2dd60..da53c0e026f0 100644
--- a/drivers/greybus/operation.c
+++ b/drivers/greybus/operation.c
@@ -1047,6 +1047,13 @@ void gb_connection_recv(struct gb_connection *connection,
 	/* Use memcpy as data may be unaligned */
 	memcpy(&header, data, sizeof(header));
 	msg_size = le16_to_cpu(header.size);
+	if (msg_size < sizeof(header)) {
+		dev_err_ratelimited(dev,
+				    "%s: invalid message header size (%zu < %zu)\n",
+				    connection->name, msg_size,
+				    sizeof(header));
+		return;
+	}
 	if (size < msg_size) {
 		dev_err_ratelimited(dev,
 				    "%s: incomplete message 0x%04x of type 0x%02x received (%zu < %zu)\n",
-- 
2.53.0

Re: [PATCH] greybus: verify the received message size covers the message header

[sashiko-bot]

> In gb_connection_recv(), the size of the received data is checked
> against sizeof(struct gb_operation_msg_hdr) and against the message
> size encoded in the header (msg_size), but msg_size itself is never
> checked against the header size.
> 
> If a peer sends a message whose header claims a size smaller than
> the header itself (e.g. header.size == 3), the two existing checks
> both pass (size >= sizeof(header) and size >= msg_size), and the
> message is dispatched with the undersized msg_size.
> 
> In gb_operation_create_incoming(), this leads to an unsigned
> integer underflow in:
> 
> 	request_size = size - sizeof(struct gb_operation_msg_hdr);
> 
> [ ... ]
> 
> Fixes: d90c25b0a279 ("greybus: let operation layer examine incoming data")
> Reported-by: syzbot+0b456664585fa81a47f6@syzkaller.appspotmail.com
> Closes: https://syzbot.org/bug?extid=0b456664585fa81a47f6
> Signed-off-by: Shunbo Shi <shishunbo@cmss.chinamobile.com>

Sashiko has reviewed this patch and found no issues.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261112082230.33584-1-shishunbo@cmss.chinamobile.com?part=1

Re: [PATCH] greybus: verify the received message size covers the message header

[Dan Carpenter]

On Thu, Nov 12, 2026 at 08:22:29AM +0000, Shunbo Shi wrote:
> In gb_connection_recv(), the size of the received data is checked
> against sizeof(struct gb_operation_msg_hdr) and against the message
> size encoded in the header (msg_size), but msg_size itself is never
> checked against the header size.
> 
> If a peer sends a message whose header claims a size smaller than
> the header itself (e.g. header.size == 3), the two existing checks
> both pass (size >= sizeof(header) and size >= msg_size), and the
> message is dispatched with the undersized msg_size.
> 
> In gb_operation_create_incoming(), this leads to an unsigned
> integer underflow in:
> 
> 	request_size = size - sizeof(struct gb_operation_msg_hdr);
> 
> The underflowed request_size then wraps back around in
> gb_operation_message_alloc():
> 
> 	message_size = payload_size + sizeof(*header);
> 
> causing kzalloc() to allocate a buffer that is too small to hold
> the message header.  When the response is later prepared in
> gb_operation_response_alloc(), reading
> request_header->operation_id reads past the end of the undersized
> allocation, triggering a KASAN slab-out-of-bounds report.  When
> header.size is zero, kzalloc(0) returns ZERO_SIZE_PTR and the
> same read dereferences an invalid address.
> 
> Verify msg_size >= sizeof(header) in gb_connection_recv() so that
> the "Caller has made sure we at least have a message header"
> assumption in gb_operation_create_incoming() actually holds.
> 
> Fixes: d90c25b0a279 ("greybus: let operation layer examine incoming data")
> Reported-by: syzbot+0b456664585fa81a47f6@syzkaller.appspotmail.com
> Closes: https://syzbot.org/bug?extid=0b456664585fa81a47f6
> Signed-off-by: Shunbo Shi <shishunbo@cmss.chinamobile.com>
> ---
>  drivers/greybus/operation.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/greybus/operation.c b/drivers/greybus/operation.c
> index 7e12ffb2dd60..da53c0e026f0 100644
> --- a/drivers/greybus/operation.c
> +++ b/drivers/greybus/operation.c
> @@ -1047,6 +1047,13 @@ void gb_connection_recv(struct gb_connection *connection,
>  	/* Use memcpy as data may be unaligned */
>  	memcpy(&header, data, sizeof(header));
>  	msg_size = le16_to_cpu(header.size);
> +	if (msg_size < sizeof(header)) {
> +		dev_err_ratelimited(dev,
> +				    "%s: invalid message header size (%zu < %zu)\n",
> +				    connection->name, msg_size,
> +				    sizeof(header));
> +		return;
> +	}
>  	if (size < msg_size) {

Combine the conditions:

	if (msg_size < sizeof(header) || msg_size > size) {

regards,
dan carpenter

>  		dev_err_ratelimited(dev,
>  				    "%s: incomplete message 0x%04x of type 0x%02x received (%zu < %zu)\n",
> -- 
> 2.53.0
> 
> 
>