syzbot


KASAN: use-after-free Read in squashfs_get_id

Status: fixed on 2021/02/19 15:06
Reported-by: syzbot+b06d57ba83f604522af2@syzkaller.appspotmail.com
Fix commit: e5099c0e851a squashfs: add more sanity checks in id lookup
First crash: 589d, last: 536d
similar bugs (2):
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-4.14 KASAN: use-after-free Read in squashfs_get_id C 1 488d 584d 1/1 fixed on 2021/02/23 13:44
upstream KASAN: use-after-free Read in squashfs_get_id C error error 6 552d 639d 0/22 upstream: reported C repro on 2020/09/25 16:12

Sample crash report:
SQUASHFS error: squashfs_read_data failed to read block 0x0
SQUASHFS error: Unable to read metadata cache entry [0]
SQUASHFS error: Unable to read inode 0x99001a
==================================================================
BUG: KASAN: use-after-free in squashfs_get_id+0x1ae/0x1d0 fs/squashfs/id.c:51
Read of size 8 at addr ffff8880b0a88780 by task syz-executor734/8129

CPU: 0 PID: 8129 Comm: syz-executor734 Not tainted 4.19.161-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1fc/0x2fe lib/dump_stack.c:118
 print_address_description.cold+0x54/0x219 mm/kasan/report.c:256
 kasan_report_error.cold+0x8a/0x1c7 mm/kasan/report.c:354
 kasan_report mm/kasan/report.c:412 [inline]
 __asan_report_load8_noabort+0x88/0x90 mm/kasan/report.c:433
 squashfs_get_id+0x1ae/0x1d0 fs/squashfs/id.c:51
 squashfs_new_inode fs/squashfs/inode.c:64 [inline]
 squashfs_read_inode+0x1b4/0x1b40 fs/squashfs/inode.c:133
 squashfs_fill_super+0x1655/0x1c00 fs/squashfs/super.c:318
 mount_bdev+0x2fc/0x3b0 fs/super.c:1158
 mount_fs+0xa3/0x30c fs/super.c:1261
 vfs_kern_mount.part.0+0x68/0x470 fs/namespace.c:961
 vfs_kern_mount fs/namespace.c:951 [inline]
 do_new_mount fs/namespace.c:2469 [inline]
 do_mount+0x113c/0x2f10 fs/namespace.c:2799
 ksys_mount+0xcf/0x130 fs/namespace.c:3015
 __do_sys_mount fs/namespace.c:3029 [inline]
 __se_sys_mount fs/namespace.c:3026 [inline]
 __x64_sys_mount+0xba/0x150 fs/namespace.c:3026
 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x447cca
Code: b8 08 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 7d a3 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 0f 83 5a a3 fb ff c3 66 0f 1f 84 00 00 00 00 00
RSP: 002b:00007ffffc0f2ad8 EFLAGS: 00000293 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007ffffc0f2b30 RCX: 0000000000447cca
RDX: 0000000020000000 RSI: 00000000200000c0 RDI: 00007ffffc0f2af0
RBP: 00007ffffc0f2af0 R08: 00007ffffc0f2b30 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000001
R13: 0000000000000004 R14: 0000000000000003 R15: 0000000000000003

Allocated by task 8129:
 __do_kmalloc mm/slab.c:3727 [inline]
 __kmalloc+0x15a/0x3c0 mm/slab.c:3736
 kmalloc_array include/linux/slab.h:637 [inline]
 kcalloc include/linux/slab.h:648 [inline]
 squashfs_read_table+0xc2/0x1e3 fs/squashfs/cache.c:430
 squashfs_read_xattr_id_table+0x2b/0x220 fs/squashfs/xattr_id.c:72
 squashfs_fill_super+0xc28/0x1c00 fs/squashfs/super.c:233
 mount_bdev+0x2fc/0x3b0 fs/super.c:1158
 mount_fs+0xa3/0x30c fs/super.c:1261
 vfs_kern_mount.part.0+0x68/0x470 fs/namespace.c:961
 vfs_kern_mount fs/namespace.c:951 [inline]
 do_new_mount fs/namespace.c:2469 [inline]
 do_mount+0x113c/0x2f10 fs/namespace.c:2799
 ksys_mount+0xcf/0x130 fs/namespace.c:3015
 __do_sys_mount fs/namespace.c:3029 [inline]
 __se_sys_mount fs/namespace.c:3026 [inline]
 __x64_sys_mount+0xba/0x150 fs/namespace.c:3026
 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 8129:
 __cache_free mm/slab.c:3503 [inline]
 kfree+0xcc/0x210 mm/slab.c:3822
 squashfs_read_table+0x191/0x1e3 fs/squashfs/cache.c:448
 squashfs_read_xattr_id_table+0x2b/0x220 fs/squashfs/xattr_id.c:72
 squashfs_fill_super+0xc28/0x1c00 fs/squashfs/super.c:233
 mount_bdev+0x2fc/0x3b0 fs/super.c:1158
 mount_fs+0xa3/0x30c fs/super.c:1261
 vfs_kern_mount.part.0+0x68/0x470 fs/namespace.c:961
 vfs_kern_mount fs/namespace.c:951 [inline]
 do_new_mount fs/namespace.c:2469 [inline]
 do_mount+0x113c/0x2f10 fs/namespace.c:2799
 ksys_mount+0xcf/0x130 fs/namespace.c:3015
 __do_sys_mount fs/namespace.c:3029 [inline]
 __se_sys_mount fs/namespace.c:3026 [inline]
 __x64_sys_mount+0xba/0x150 fs/namespace.c:3026
 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8880b0a88780
 which belongs to the cache kmalloc-32 of size 32
The buggy address is located 0 bytes inside of
 32-byte region [ffff8880b0a88780, ffff8880b0a887a0)
The buggy address belongs to the page:
page:ffffea0002c2a200 count:1 mapcount:0 mapping:ffff88813bff01c0 index:0xffff8880b0a88fc1
flags: 0xfff00000000100(slab)
raw: 00fff00000000100 ffffea0002c2ee08 ffffea0002bff148 ffff88813bff01c0
raw: ffff8880b0a88fc1 ffff8880b0a88000 000000010000003f 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880b0a88680: fb fb fb fb fc fc fc fc 00 fc fc fc fc fc fc fc
 ffff8880b0a88700: 00 fc fc fc fc fc fc fc 00 00 fc fc fc fc fc fc
>ffff8880b0a88780: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
                   ^
 ffff8880b0a88800: fb fb fb fb fc fc fc fc 00 00 fc fc fc fc fc fc
 ffff8880b0a88880: fb fb fb fb fc fc fc fc 00 00 fc fc fc fc fc fc
==================================================================

Fix bisection attempts:
Manager Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Title
ci2-linux-4-19 2021/01/06 18:18 linux-4.19.y 4143d798313f f80ce148 .config log report syz C
Crashes (3):
Manager Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Title
ci2-linux-4-19 2020/12/07 16:22 linux-4.19.y daefdc9eb24b f80ce148 .config log report syz C
ci2-linux-4-19 2020/11/14 09:28 linux-4.19.y 31acccdc8774 1bf9a662 .config log report syz C
ci2-linux-4-19 2020/11/14 09:13 linux-4.19.y 31acccdc8774 1bf9a662 .config log report info