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

Hello,

syzbot found the following issue on:

HEAD commit:    21d6ac051080 Merge branch 'for-next/core' into for-kernelci
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
console output: https://syzkaller.appspot.com/x/log.txt?x=163ad6c6580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=d1128bc53f2ef7f3
dashboard link: https://syzkaller.appspot.com/bug?extid=3a0d6aa450317f25e501
compiler:       Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
userspace arch: arm64
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10cbfa79580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1182d949580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/88380e2ddcb9/disk-21d6ac05.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/5dba5c2896b7/vmlinux-21d6ac05.xz
kernel image: https://storage.googleapis.com/syzbot-assets/52ac739e37e0/Image-21d6ac05.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email protected]

==================================================================
BUG: KASAN: slab-out-of-bounds in gether_get_ifname+0x104/0x124 drivers/usb/gadget/function/u_ether.c:1033
Read of size 1 at addr ffff0000d09b5042 by task syz.0.17/4928

CPU: 1 UID: 0 PID: 4928 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/07/2026
Call trace:
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:499 (C)
 __dump_stack+0x30/0x40 lib/dump_stack.c:94
 dump_stack_lvl+0xd8/0x12c lib/dump_stack.c:120
 print_address_description+0xb0/0x238 mm/kasan/report.c:378
 print_report+0x68/0x84 mm/kasan/report.c:482
 kasan_report+0x8c/0xc4 mm/kasan/report.c:595
 __asan_report_load1_noabort+0x20/0x2c mm/kasan/report_generic.c:378
 gether_get_ifname+0x104/0x124 drivers/usb/gadget/function/u_ether.c:1033
 f_phonet_ifname_show+0x4c/0x60 drivers/usb/gadget/function/f_phonet.c:603
 fill_read_buffer fs/configfs/file.c:68 [inline]
 configfs_read_iter+0x234/0x508 fs/configfs/file.c:88
 new_sync_read fs/read_write.c:493 [inline]
 vfs_read+0x498/0x8c8 fs/read_write.c:574
 ksys_read+0x12c/0x228 fs/read_write.c:716
 __do_sys_read fs/read_write.c:725 [inline]
 __se_sys_read fs/read_write.c:723 [inline]
 __arm64_sys_read+0x84/0x98 fs/read_write.c:723
 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
 invoke_syscall+0x98/0x244 arch/arm64/kernel/syscall.c:49
 el0_svc_common+0xec/0x23c arch/arm64/kernel/syscall.c:121
 do_el0_svc+0x4c/0x5c arch/arm64/kernel/syscall.c:140
 el0_svc+0x64/0x260 arch/arm64/kernel/entry-common.c:758
 el0t_64_sync_handler+0x44/0x104 arch/arm64/kernel/entry-common.c:777
 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:590

Allocated by task 4928:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x40/0x78 mm/kasan/common.c:78
 kasan_save_alloc_info+0x40/0x50 mm/kasan/generic.c:570
 poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
 __kasan_kmalloc+0x9c/0xb4 mm/kasan/common.c:415
 kasan_kmalloc include/linux/kasan.h:263 [inline]
 __do_kmalloc_node mm/slub.c:5334 [inline]
 __kvmalloc_node_noprof+0x460/0x7d8 mm/slub.c:6905
 alloc_netdev_mqs+0xac/0xf2c net/core/dev.c:12055
 gphonet_setup_default+0x38/0x88 drivers/usb/gadget/function/f_phonet.c:706
 phonet_alloc_inst+0x84/0x100 drivers/usb/gadget/function/f_phonet.c:640
 try_get_usb_function_instance+0xe4/0x164 drivers/usb/gadget/functions.c:28
 usb_get_function_instance+0x24/0xb0 drivers/usb/gadget/functions.c:44
 function_make+0x110/0x300 drivers/usb/gadget/configfs.c:626
 configfs_mkdir+0x374/0x7d4 fs/configfs/dir.c:1360
 vfs_mkdir+0x2dc/0x464 fs/namei.c:5276
 filename_mkdirat+0x228/0x3f4 fs/namei.c:5309
 __do_sys_mkdirat fs/namei.c:5330 [inline]
 __se_sys_mkdirat fs/namei.c:5327 [inline]
 __arm64_sys_mkdirat+0x9c/0xc0 fs/namei.c:5327
 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
 invoke_syscall+0x98/0x244 arch/arm64/kernel/syscall.c:49
 el0_svc_common+0xec/0x23c arch/arm64/kernel/syscall.c:121
 do_el0_svc+0x4c/0x5c arch/arm64/kernel/syscall.c:140
 el0_svc+0x64/0x260 arch/arm64/kernel/entry-common.c:758
 el0t_64_sync_handler+0x44/0x104 arch/arm64/kernel/entry-common.c:777
 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:590

The buggy address belongs to the object at ffff0000d09b4000
 which belongs to the cache kmalloc-cg-4k of size 4096
The buggy address is located 314 bytes to the right of
 allocated 3848-byte region [ffff0000d09b4000, ffff0000d09b4f08)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1109b0
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
memcg:ffff0000cb462741
flags: 0x5ffc00000000040(head|node=0|zone=2|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 05ffc00000000040 ffff0000c000b500 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800040004 00000000f5000000 ffff0000cb462741
head: 05ffc00000000040 ffff0000c000b500 dead000000000100 dead000000000122
head: 0000000000000000 0000000800040004 00000000f5000000 ffff0000cb462741
head: 05ffc00000000003 fffffdffc3426c01 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff0000d09b4f00: 00 fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff0000d09b4f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff0000d09b5000: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                                           ^
 ffff0000d09b5080: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff0000d09b5100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================


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