Subject: [syzbot] BUG: unable to handle kernel paging request in p9_client_prepare_req

From: syzbot <[email-masked]>
Date: Wed, 16 Nov 2022 11:49:38 -0800

Hello,

syzbot found the following issue on:

HEAD commit:    9500fc6e9e60 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=13bdf3f1880000
kernel config:  https://syzkaller.appspot.com/x/.config?x=b25c9f218686dd5e
dashboard link: https://syzkaller.appspot.com/bug?extid=69c3bf057b7a81f47758
compiler:       Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2
userspace arch: arm64
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17f6d5cd880000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=154f2a45880000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/1363e60652f7/disk-9500fc6e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/fcc4da811bb6/vmlinux-9500fc6e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/0b554298f1fa/Image-9500fc6e.gz.xz

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

Unable to handle kernel paging request at virtual address bf908d5e7640333a
Mem abort info:
  ESR = 0x0000000096000004
  EC = 0x25: DABT (current EL), IL = 32 bits
  SET = 0, FnV = 0
  EA = 0, S1PTW = 0
  FSC = 0x04: level 0 translation fault
Data abort info:
  ISV = 0, ISS = 0x00000004
  CM = 0, WnR = 0
[bf908d5e7640333a] address between user and kernel address ranges
Internal error: Oops: 0000000096000004 [#1] PREEMPT SMP
Modules linked in:
CPU: 0 PID: 3084 Comm: syz-executor291 Not tainted 6.1.0-rc5-syzkaller-32269-g9500fc6e9e60 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/30/2022
pstate: 40400005 (nZcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : __kmem_cache_alloc_node+0x17c/0x350 mm/slub.c:3437
lr : slab_pre_alloc_hook mm/slab.h:712 [inline]
lr : slab_alloc_node mm/slub.c:3318 [inline]
lr : __kmem_cache_alloc_node+0x80/0x350 mm/slub.c:3437
sp : ffff80000ff636c0
x29: ffff80000ff636d0 x28: ffff0000c9848000 x27: 0000000000000000
x26: 0000000000001000 x25: 00000000ffffffff x24: ffff80000bea07bc
x23: 0000000000001000 x22: bf908d5e76402b3a x21: 0000000000000000
x20: 0000000000000c40 x19: ffff0000c0001700 x18: 000000000000ba7e
x17: 000000000000b67e x16: ffff80000dc18158 x15: ffff0000c9848000
x14: 0000000000000010 x13: 0000000000000000 x12: ffff0000c9848000
x11: 0000000000000001 x10: 0000000000000000 x9 : 0000000000000800
x8 : 00000000000613f9 x7 : ffff8000084c0640 x6 : 0000000000000000
x5 : 0000000000000000 x4 : 0000000000000001 x3 : 0000000000061401
x2 : 0000000000000000 x1 : 0000000000000c40 x0 : fffffc00032ed000
Call trace:
 next_tid mm/slub.c:2349 [inline]
 slab_alloc_node mm/slub.c:3382 [inline]
 __kmem_cache_alloc_node+0x17c/0x350 mm/slub.c:3437
 __do_kmalloc_node mm/slab_common.c:954 [inline]
 __kmalloc+0xb4/0x140 mm/slab_common.c:968
 kmalloc include/linux/slab.h:558 [inline]
 p9_fcall_init net/9p/client.c:228 [inline]
 p9_tag_alloc net/9p/client.c:293 [inline]
 p9_client_prepare_req+0x2b0/0x53c net/9p/client.c:631
 p9_client_rpc+0xbc/0x548 net/9p/client.c:678
 p9_client_flush+0x118/0x1b0 net/9p/client.c:596
 p9_client_rpc+0x4cc/0x548 net/9p/client.c:724
 p9_client_create+0x4d8/0x758 net/9p/client.c:1015
 v9fs_session_init+0xa4/0x9f0 fs/9p/v9fs.c:408
 v9fs_mount+0x6c/0x568 fs/9p/vfs_super.c:126
 legacy_get_tree+0x30/0x74 fs/fs_context.c:610
 vfs_get_tree+0x40/0x140 fs/super.c:1531
 do_new_mount+0x1dc/0x4e4 fs/namespace.c:3040
 path_mount+0x358/0x890 fs/namespace.c:3370
 do_mount fs/namespace.c:3383 [inline]
 __do_sys_mount fs/namespace.c:3591 [inline]
 __se_sys_mount fs/namespace.c:3568 [inline]
 __arm64_sys_mount+0x2c4/0x3c4 fs/namespace.c:3568
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall arch/arm64/kernel/syscall.c:52 [inline]
 el0_svc_common+0x138/0x220 arch/arm64/kernel/syscall.c:142
 do_el0_svc+0x48/0x164 arch/arm64/kernel/syscall.c:206
 el0_svc+0x58/0x150 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:584
Code: 54000ee1 34000eeb b9402a69 91002103 (f8696ada) 
---[ end trace 0000000000000000 ]---
----------------
Code disassembly (best guess):
   0:	54000ee1 	b.ne	0x1dc  // b.any
   4:	34000eeb 	cbz	w11, 0x1e0
   8:	b9402a69 	ldr	w9, [x19, #40]
   c:	91002103 	add	x3, x8, #0x8
* 10:	f8696ada 	ldr	x26, [x22, x9] <-- trapping instruction

---
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