[syzbot] [kernel?] KASAN: global-out-of-bounds Read in uevent_store

[syzbot] [kernel?] KASAN: global-out-of-bounds Read in uevent_store

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    9d2ed026f031 Merge tag 'sysctl-7.03-rc1' of git://git.kern..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13921e79580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=996f19b48f3c7123
dashboard link: https://syzkaller.appspot.com/bug?extid=d164947c037324221043
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=164f5e79580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-9d2ed026.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/dbab070bbde5/vmlinux-9d2ed026.xz
kernel image: https://storage.googleapis.com/syzbot-assets/857014a70033/bzImage-9d2ed026.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d164947c037324221043@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: global-out-of-bounds in kobject_action_type lib/kobject_uevent.c:86 [inline]
BUG: KASAN: global-out-of-bounds in kobject_synth_uevent+0x79d/0x7d0 lib/kobject_uevent.c:200
Read of size 1 at addr ffffffff8d7101be by task syz.0.17/5909

CPU: 3 UID: 0 PID: 5909 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
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
 kobject_action_type lib/kobject_uevent.c:86 [inline]
 kobject_synth_uevent+0x79d/0x7d0 lib/kobject_uevent.c:200
 uevent_store+0x46/0x90 drivers/base/bus.c:723
 drv_attr_store+0x74/0xb0 drivers/base/bus.c:125
 sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:145
 kernfs_fop_write_iter+0x3e0/0x5f0 fs/kernfs/file.c:345
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x6af/0x1050 fs/read_write.c:687
 ksys_write+0x12a/0x250 fs/read_write.c:739
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f044c59e0d9
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:00007ffd04c3e3e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f044c825fa0 RCX: 00007f044c59e0d9
RDX: 000000000000003f RSI: 0000200000000300 RDI: 0000000000000003
RBP: 00007f044c635024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f044c825fac R14: 00007f044c825fa0 R15: 00007f044c825fa0
 </TASK>

The buggy address belongs to the variable:
 uevent_helper_sysctl_table+0xde/0x2a0

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0xd710
flags: 0xfff00000002000(reserved|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000002000 ffffea000035c408 ffffea000035c408 0000000000000000
raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner info is not present (never set?)

Memory state around the buggy address:
 ffffffff8d710080: f9 f9 f9 f9 00 f9 f9 f9 f9 f9 f9 f9 00 00 00 00
 ffffffff8d710100: 00 00 00 f9 f9 f9 f9 f9 00 07 f9 f9 f9 f9 f9 f9
>ffffffff8d710180: 04 f9 f9 f9 f9 f9 f9 f9 07 f9 f9 f9 f9 f9 f9 f9
                                        ^
 ffffffff8d710200: 07 f9 f9 f9 f9 f9 f9 f9 05 f9 f9 f9 f9 f9 f9 f9
 ffffffff8d710280: 07 f9 f9 f9 f9 f9 f9 f9 00 f9 f9 f9 f9 f9 f9 f9
==================================================================


---
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[syzbot] [kernel?] KASAN: global-out-of-bounds Read in uevent_store

[Jeffin Philip]

#syz test upstream

diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c
index ddbc4d7482d2..b03562301bfe 100644
--- a/lib/kobject_uevent.c
+++ b/lib/kobject_uevent.c
@@ -83,7 +83,7 @@ static int kobject_action_type(const char *buf, size_t count,
 	for (action = 0; action < ARRAY_SIZE(kobject_actions); action++) {
 		if (strncmp(kobject_actions[action], buf, count_first) != 0)
 			continue;
-		if (kobject_actions[action][count_first] != '\0')
+		if (strlen(kobject_actions[action]) != count_first)
 			continue;
 		if (args)
 			*args = args_start;

Re: [syzbot] [kernel?] KASAN: global-out-of-bounds Read in uevent_store

[syzbot]

> #syz test upstream

I've failed to parse your command.
Did you perhaps forget to provide the branch name, or added an extra ':'?
Please use one of the two supported formats:
1. #syz test
2. #syz test: repo branch-or-commit-hash
Note the lack of ':' in option 1.

>
> diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c
> index ddbc4d7482d2..b03562301bfe 100644
> --- a/lib/kobject_uevent.c
> +++ b/lib/kobject_uevent.c
> @@ -83,7 +83,7 @@ static int kobject_action_type(const char *buf, size_t count,
>  	for (action = 0; action < ARRAY_SIZE(kobject_actions); action++) {
>  		if (strncmp(kobject_actions[action], buf, count_first) != 0)
>  			continue;
> -		if (kobject_actions[action][count_first] != '\0')
> +		if (strlen(kobject_actions[action]) != count_first)
>  			continue;
>  		if (args)
>  			*args = args_start;

[syzbot] [kernel?] KASAN: global-out-of-bounds Read in uevent_store

[Jeffin Philip]

#syz test: upstream 9d2ed026f031

diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c
index ddbc4d7482d2..b03562301bfe 100644
--- a/lib/kobject_uevent.c
+++ b/lib/kobject_uevent.c
@@ -83,7 +83,7 @@ static int kobject_action_type(const char *buf, size_t count,
 	for (action = 0; action < ARRAY_SIZE(kobject_actions); action++) {
 		if (strncmp(kobject_actions[action], buf, count_first) != 0)
 			continue;
-		if (kobject_actions[action][count_first] != '\0')
+		if (strlen(kobject_actions[action]) != count_first)
 			continue;
 		if (args)
 			*args = args_start;

Re: [syzbot] [kernel?] KASAN: global-out-of-bounds Read in uevent_store

[Greg KH]

On Mon, Aug 24, 2026 at 12:37:48PM +0530, Jeffin Philip wrote:
> #syz test upstream
> 
> diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c
> index ddbc4d7482d2..b03562301bfe 100644
> --- a/lib/kobject_uevent.c
> +++ b/lib/kobject_uevent.c
> @@ -83,7 +83,7 @@ static int kobject_action_type(const char *buf, size_t count,
>  	for (action = 0; action < ARRAY_SIZE(kobject_actions); action++) {
>  		if (strncmp(kobject_actions[action], buf, count_first) != 0)
>  			continue;
> -		if (kobject_actions[action][count_first] != '\0')
> +		if (strlen(kobject_actions[action]) != count_first)
>  			continue;
>  		if (args)
>  			*args = args_start;
> 

Why not look at this patch:
	https://lore.kernel.org/r/200d27f7.1471a.1a0138c92da.Coremail.stitch@zju.edu.cn

Re: [syzbot] [kernel?] KASAN: global-out-of-bounds Read in uevent_store

[syzbot]

Hello,

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

Reported-by: syzbot+d164947c037324221043@syzkaller.appspotmail.com
Tested-by: syzbot+d164947c037324221043@syzkaller.appspotmail.com

Tested on:

commit:         9d2ed026 Merge tag 'sysctl-7.03-rc1' of git://git.kern..
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=12f66415580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=996f19b48f3c7123
dashboard link: https://syzkaller.appspot.com/bug?extid=d164947c037324221043
compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
patch:          https://syzkaller.appspot.com/x/patch.diff?x=14e91179580000

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