Re: [syzbot] [mm?] WARNING in ep_write_iter

On Mon Aug 17, 2026 at 5:14 AM EDT, syzbot wrote:
> syzbot has found a reproducer for the following issue on:
>
> HEAD commit:    8d3ae59288f1 Linux 7.2
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=13bad949580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=1d67342c314f228d
> dashboard link: https://syzkaller.appspot.com/bug?extid=805630f1453e490427fa
> compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1637ea25580000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: [email protected]
>
> gadgetfs: bound to dummy_udc driver
> ------------[ cut here ]------------
> 1
> WARNING: mm/page_alloc.c:5280 at __alloc_frozen_pages_noprof+0x2427/0x2dc0 mm/page_alloc.c:5280, CPU#2: syz-executor421/6034
> Modules linked in:
> CPU: 2 UID: 0 PID: 6034 Comm: syz-executor421 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
> RIP: 0010:__alloc_frozen_pages_noprof+0x2427/0x2dc0 mm/page_alloc.c:5280
> Code: e9 8d fb ff ff 31 d2 be 28 12 00 00 48 c7 c7 a0 74 01 8c e8 7b 95 68 ff 2e 2e 2e 31 c0 e9 02 ed ff ff c6 05 85 90 bc 0e 01 90 <0f> 0b 90 e9 6f df ff ff 48 c7 c7 80 be f3 8e 45 89 f7 44 8b 74 24
> RSP: 0018:ffffc900048c7810 EFLAGS: 00010246
> RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: 1ffff92000918f1c RDI: 0000000000040cc0
> RBP: 0000000000000013 R08: 0000000000000005 R09: 0000000000000009
> R10: 0000000000000013 R11: 0000000000000000 R12: 0000000000040cc0
> R13: 1ffff92000918f5a R14: ffffffff9b95c444 R15: 0000000000000001
> FS:  00005555738a6400(0000) GS:ffff8880d5dde000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007ffd5f5d6fe8 CR3: 0000000020943000 CR4: 0000000000352ef0
> Call Trace:
>  <TASK>
>  alloc_pages_mpol+0x1fb/0x540 mm/mempolicy.c:2490
>  ___kmalloc_large_node+0xe5/0x120 mm/slub.c:5274
>  __kmalloc_large_node_noprof+0x1c/0x70 mm/slub.c:5305
>  __do_kmalloc_node mm/slub.c:5322 [inline]
>  __kmalloc_noprof+0x5a1/0x820 mm/slub.c:5359
>  _kmalloc_noprof include/linux/slab.h:992 [inline]
>  ep_write_iter+0x180/0xbc0 drivers/usb/gadget/legacy/inode.c:669
>  new_sync_write fs/read_write.c:595 [inline]
>  vfs_write+0x6ac/0x1050 fs/read_write.c:687
>  ksys_write+0x12a/0x250 fs/read_write.c:739
>  do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
>  do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7f7cc18b5cb7
> Code: 48 89 fa 4c 89 df e8 98 1d 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff
> RSP: 002b:00007ffd5f5d76e0 EFLAGS: 00000202 ORIG_RAX: 0000000000000001
> RAX: ffffffffffffffda RBX: 00005555738a6400 RCX: 00007f7cc18b5cb7
> RDX: 000000007fffffff RSI: 0000000000000000 RDI: 0000000000000004
> RBP: 00007ffd5f5d7730 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000202 R12: 00007ffd5f5d7930
> R13: 00007f7cc18ea039 R14: 00007ffd5f5d7b30 R15: 0000000000000002
>  </TASK>
>
>
> ---
> If you want syzbot to run the reproducer, reply with:
> #syz test: git://repo/address.git branch-or-commit-hash
> If you attach or paste a git patch, syzbot will apply it before testing.


#syz test


diff --git a/mm/slub.c b/mm/slub.c
index 0337e60db5ace..2d87896c6dfbf 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -5265,6 +5265,9 @@ static void *___kmalloc_large_node(size_t size, gfp_t flags, int node)
 	void *ptr = NULL;
 	unsigned int order = get_order(size);
 
+	if (size > KMALLOC_MAX_SIZE)
+		return NULL;
+
 	if (unlikely(flags & GFP_SLAB_BUG_MASK))
 		flags = kmalloc_fix_flags(flags);
 


-- 
Best Regards,
Yan, Zi