[syzbot] [bcachefs?] KASAN: use-after-free Read in poly1305_update

[syzbot <syzbot+bfaeaa8e26281970158d@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    19272b37aa4f Linux 6.16-rc1
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=159ab9d4580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8409c4d4e51ac27
dashboard link: https://syzkaller.appspot.com/bug?extid=bfaeaa8e26281970158d
compiler:       Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6
userspace arch: arm64
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15c3f682580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1340310c580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/92d22b0c6493/disk-19272b37.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/3fb0142bb63a/vmlinux-19272b37.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3d5f3836ae42/Image-19272b37.gz.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/d19ea34ad935/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+bfaeaa8e26281970158d@syzkaller.appspotmail.com

  ret fsck_errors_not_fixed
bcachefs (loop0): error reading btree root btree=xattrs level=0: btree_node_read_error, fixing
==================================================================
BUG: KASAN: use-after-free in poly1305_update+0x138/0x188 lib/crypto/poly1305.c:44
Read of size 8 at addr ffff0000e4b60070 by task syz-executor339/6486

CPU: 1 UID: 0 PID: 6486 Comm: syz-executor339 Not tainted 6.16.0-rc1-syzkaller-g19272b37aa4f #0 PREEMPT 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call trace:
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:466 (C)
 __dump_stack+0x30/0x40 lib/dump_stack.c:94
 dump_stack_lvl+0xd8/0x12c lib/dump_stack.c:120
 print_address_description+0xa8/0x254 mm/kasan/report.c:408
 print_report+0x68/0x84 mm/kasan/report.c:521
 kasan_report+0xb0/0x110 mm/kasan/report.c:634
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x264/0x2a4 mm/kasan/generic.c:189
 __asan_memcpy+0x3c/0x84 mm/kasan/shadow.c:105
 poly1305_update+0x138/0x188 lib/crypto/poly1305.c:44
 bch2_checksum+0x1d4/0x4ac fs/bcachefs/checksum.c:157
 bch2_btree_node_read_done+0x968/0x432c fs/bcachefs/btree_io.c:1148
 btree_node_read_work+0x328/0xc1c fs/bcachefs/btree_io.c:1399
 bch2_btree_node_read+0x814/0x23f8 fs/bcachefs/btree_io.c:-1
 __bch2_btree_root_read fs/bcachefs/btree_io.c:1865 [inline]
 bch2_btree_root_read+0x280/0x3c8 fs/bcachefs/btree_io.c:1887
 read_btree_roots+0x218/0x6bc fs/bcachefs/recovery.c:591
 bch2_fs_recovery+0x1d1c/0x2fd4 fs/bcachefs/recovery.c:964
 bch2_fs_start+0x914/0xbc0 fs/bcachefs/super.c:1200
 bch2_fs_get_tree+0x890/0xfd0 fs/bcachefs/fs.c:2489
 vfs_get_tree+0x90/0x28c fs/super.c:1802
 do_new_mount+0x228/0x814 fs/namespace.c:3885
 path_mount+0x5b4/0xde0 fs/namespace.c:4209
 do_mount fs/namespace.c:4222 [inline]
 __do_sys_mount fs/namespace.c:4433 [inline]
 __se_sys_mount fs/namespace.c:4410 [inline]
 __arm64_sys_mount+0x3e8/0x468 fs/namespace.c:4410
 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
 invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49
 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132
 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
 el0_svc+0x58/0x17c arch/arm64/kernel/entry-common.c:767
 el0t_64_sync_handler+0x78/0x108 arch/arm64/kernel/entry-common.c:786
 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:600

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x124b60
flags: 0x5ffc00000000000(node=0|zone=2|lastcpupid=0x7ff)
raw: 05ffc00000000000 fffffdffc392d808 fffffdffc392d808 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff0000e4b5ff00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff0000e4b5ff80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff0000e4b60000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                                             ^
 ffff0000e4b60080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff0000e4b60100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
bcachefs (loop0): btree node read error at btree alloc level 0/0
  u64s 11 type btree_ptr_v2 U64_MAX:18446744073709551365:U32_MAX len 0 ver 0: seq 1818ce08861e3527 written 40 min_key POS_MIN durability: 1 ptr: 0:26:0 gen 0
  loop0 node offset 0/40 bset u64s 65531: checksum error, type chacha20_poly1305_128: got d1207b6f1073532ce6802ea238ac7a29 should be a1c0cae4d1c6eac9087fba7ada6f601b
  flagging btree alloc lost data
  running recovery pass check_alloc_info (13), currently at recovery_pass_empty (0)
  ret fsck_errors_not_fixed
bcachefs (loop0): error reading btree root btree=alloc level=0: btree_node_read_error, fixing
bcachefs (loop0): btree node read error at btree freespace level 0/0
  u64s 11 type btree_ptr_v2 SPOS_MAX len 0 ver 0: seq b6c44d07df4e9bb7 written 48 min_key POS_MIN durability: 1 ptr: 0:29:0 gen 0
  loop0 node offset 8/48 bset u64s 35: checksum error, type chacha20_poly1305_128: got ed761e9f1d4c73c28012c6926fffa8ec should be 696606121d98d113a1b1dc69c6e72339
  flagging btree freespace lost data
  ret fsck_errors_not_fixed
bcachefs (loop0): error reading btree root btree=freespace level=0: btree_node_read_error, fixing
bcachefs (loop0): btree node read error at btree backpointers level 0/0
  u64s 11 type btree_ptr_v2 SPOS_MAX len 0 ver 0: seq 3b468546fb27822d written 24 min_key POS_MIN durability: 1 ptr: 0:36:0 gen 0
  loop0 node offset 16/24 bset u64s 14: checksum error, type chacha20_poly1305_128: got a67d0bb2ddad47adce7ef65cfcb4dbe2 should be 6399ef4aeb6d8a4369c39b0b9ed27362
  flagging btree backpointers lost data
  running recovery pass check_btree_backpointers (15), currently at recovery_pass_empty (0)
  ret fsck_errors_not_fixed
bcachefs (loop0): error reading btree root btree=backpointers level=0: btree_node_read_error, fixing
bcachefs (loop0): scan_for_btree_nodes...
bcachefs (loop0): btree node scan found 7 nodes after overwrites
 done
bcachefs (loop0): check_topology...
bcachefs (loop0): btree root inodes unreadable, must recover from scan
bcachefs (loop0): bch2_get_scanned_nodes(): recovery btree=inodes level=0 POS_MIN - SPOS_MAX
bcachefs (loop0): bch2_get_scanned_nodes(): recovering u64s 11 type btree_ptr_v2 SPOS_MAX len 0 ver 0: seq 2a20405ac3f40602 written 24 min_key POS_MIN durability: 1 ptr: 0:38:0 gen 0
bcachefs (loop0): empty interior btree node at btree=inodes level=1
  u64s 5 type btree_ptr SPOS_MAX len 0 ver 0, fixing
bcachefs (loop0): empty btree root inodes
bcachefs (loop0): btree root dirents unreadable, must recover from scan
bcachefs (loop0): bch2_get_scanned_nodes(): recovery btree=dirents level=0 POS_MIN - SPOS_MAX
bcachefs (loop0): bch2_get_scanned_nodes(): recovering u64s 11 type btree_ptr_v2 SPOS_MAX len 0 ver 0: seq 267fcf747c875937 written 24 min_key POS_MIN durability: 1 ptr: 0:41:0 gen 0
bcachefs (loop0): empty interior btree node at btree=dirents level=1
  u64s 5 type btree_ptr SPOS_MAX len 0 ver 0, fixing
bcachefs (loop0): empty btree root dirents
bcachefs (loop0): btree root xattrs unreadable, must recover from scan
bcachefs (loop0): bch2_get_scanned_nodes(): recovery btree=xattrs level=0 POS_MIN - SPOS_MAX
bcachefs (loop0): bch2_get_scanned_nodes(): recovering u64s 11 type btree_ptr_v2 SPOS_MAX len 0 ver 0: seq 1b881868e2a6abe1 written 16 min_key POS_MIN durability: 1 ptr: 0:31:0 gen 0
bcachefs (loop0): empty interior btree node at btree=xattrs level=1
  u64s 5 type btree_ptr SPOS_MAX len 0 ver 0, fixing
bcachefs (loop0): empty btree root xattrs
 done
bcachefs (loop0): scan_for_btree_nodes... done
bcachefs (loop0): accounting_read... done
bcachefs (loop0): alloc_read... done
bcachefs (loop0): snapshots_read... done
bcachefs (loop0): Fixed errors, running fsck a second time to verify fs is clean
bcachefs (loop0): done starting filesystem
bcachefs (loop0): missing subvolume 1
bcachefs (loop0): bch2_fs_get_tree(): error mounting: error getting root inode ENOENT_bkey_type_mismatch
bcachefs (loop0): shutting down
bcachefs (loop0): shutdown complete
bcachefs: bch2_fs_get_tree() error: ENOENT_bkey_type_mismatch


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