[syzbot] [bcachefs?] UBSAN: shift-out-of-bounds in bch2_bkey_format_invalid

[syzbot] [bcachefs?] UBSAN: shift-out-of-bounds in bch2_bkey_format_invalid

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    9221b2819b8a Add linux-next specific files for 20240503
git tree:       linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=153b20e4980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8ab537f51a6a0d98
dashboard link: https://syzkaller.appspot.com/bug?extid=9833a1d29d4a44361e2c
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=114b7a50980000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=11b7ae87180000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/3e67dbdc3c37/disk-9221b281.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ade618fa19f8/vmlinux-9221b281.xz
kernel image: https://storage.googleapis.com/syzbot-assets/df12e5073c97/bzImage-9221b281.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/d64ba6155455/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9833a1d29d4a44361e2c@syzkaller.appspotmail.com

loop0: detected capacity change from 0 to 32768
bcachefs (loop0): mounting version 1.7: mi_btree_bitmap opts=compression=lz4,nojournal_transaction_names
bcachefs (loop0): recovering from clean shutdown, journal seq 7
------------[ cut here ]------------
UBSAN: shift-out-of-bounds in fs/bcachefs/bkey.c:663:22
shift exponent 254 is too large for 64-bit type 'unsigned long long'
CPU: 1 PID: 5092 Comm: syz-executor406 Not tainted 6.9.0-rc6-next-20240503-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
 ubsan_epilogue lib/ubsan.c:231 [inline]
 __ubsan_handle_shift_out_of_bounds+0x3c8/0x420 lib/ubsan.c:468
 bch2_bkey_format_invalid+0x46c/0x5c0 fs/bcachefs/bkey.c:663
 validate_bset+0x168d/0x25a0 fs/bcachefs/btree_io.c:824
 bch2_btree_node_read_done+0x20d2/0x5ed0 fs/bcachefs/btree_io.c:1142
 btree_node_read_work+0x665/0x1300 fs/bcachefs/btree_io.c:1345
 bch2_btree_node_read+0x2637/0x2c80 fs/bcachefs/btree_io.c:1730
 __bch2_btree_root_read fs/bcachefs/btree_io.c:1769 [inline]
 bch2_btree_root_read+0x61e/0x970 fs/bcachefs/btree_io.c:1793
 read_btree_roots+0x22d/0x7b0 fs/bcachefs/recovery.c:472
 bch2_fs_recovery+0x2334/0x36e0 fs/bcachefs/recovery.c:800
 bch2_fs_start+0x356/0x5b0 fs/bcachefs/super.c:1030
 bch2_fs_open+0xa8d/0xdf0 fs/bcachefs/super.c:2105
 bch2_mount+0x71d/0x1320 fs/bcachefs/fs.c:1917
 legacy_get_tree+0xee/0x190 fs/fs_context.c:662
 vfs_get_tree+0x90/0x2a0 fs/super.c:1780
 do_new_mount+0x2be/0xb40 fs/namespace.c:3352
 do_mount fs/namespace.c:3692 [inline]
 __do_sys_mount fs/namespace.c:3898 [inline]
 __se_sys_mount+0x2d9/0x3c0 fs/namespace.c:3875
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fa35434c8fa
Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 5e 04 00 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff2b30e848 EFLAGS: 00000282 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fff2b30e860 RCX: 00007fa35434c8fa
RDX: 0000000020005d80 RSI: 0000000020005dc0 RDI: 00007fff2b30e860
RBP: 0000000000000010 R08: 00007fff2b30e8a0 R09: 0000000000005d8f
R10: 0000000000000010 R11: 0000000000000282 R12: 0000000000000004
R13: 00007fff2b30e8a0 R14: 0000000000000003 R15: 0000000001000000
 </TASK>
---[ end trace ]---


---
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Re: [syzbot] [PATCH] bcachefs: guard against invalid bits_per_field in bch2_bkey_format_invalid

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org.

***

Subject: [PATCH] bcachefs: guard against invalid bits_per_field in bch2_bkey_format_invalid
Author: cam.alvarez.i@gmail.com

#syz test
git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
A check for a valid value for bits_per_field is performed for each field before computing packed_max.
If bits_per_field is invalid for any field the whole format is deemed
invalid.

Signed-off-by: Camila Alvarez <cam.alvarez.i@gmail.com>
---
 fs/bcachefs/bcachefs_format.h |  8 ++++++++
 fs/bcachefs/bkey.c            | 17 +++++++++++++++--
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/fs/bcachefs/bcachefs_format.h b/fs/bcachefs/bcachefs_format.h
index d5b90439e581..23eb04148724 100644
--- a/fs/bcachefs/bcachefs_format.h
+++ b/fs/bcachefs/bcachefs_format.h
@@ -318,6 +318,14 @@ enum bch_bkey_fields {
 #define bkey_format_field(name, field)					\
 	[BKEY_FIELD_##name] = (sizeof(((struct bkey *) NULL)->field) * 8)
 
+#define BCH_BKEY_FIELDS()						\
+	x(INODE,        p.inode)					\
+	x(OFFSET,       p.offset)					\
+	x(SNAPSHOT,     p.snapshot)					\
+	x(SIZE,         size)						\
+	x(VERSION_HI,   version.hi)					\
+	x(VERSION_LO,   version.lo)					
+
 #define BKEY_FORMAT_CURRENT						\
 ((struct bkey_format) {							\
 	.key_u64s	= BKEY_U64s,					\
diff --git a/fs/bcachefs/bkey.c b/fs/bcachefs/bkey.c
index 76e79a15ba08..b6004b5f77e0 100644
--- a/fs/bcachefs/bkey.c
+++ b/fs/bcachefs/bkey.c
@@ -638,6 +638,13 @@ struct bkey_format bch2_bkey_format_done(struct bkey_format_state *s)
 	return ret;
 }
 
+static unsigned bch2_max_bits_per_field[] = {
+#define x(name, field) \
+	bkey_format_field(name, field),
+	BCH_BKEY_FIELDS()
+#undef x
+};
+
 int bch2_bkey_format_invalid(struct bch_fs *c,
 			     struct bkey_format *f,
 			     enum bkey_invalid_flags flags,
@@ -659,8 +666,14 @@ int bch2_bkey_format_invalid(struct bch_fs *c,
 		if (!c || c->sb.version_min >= bcachefs_metadata_version_snapshot) {
 			unsigned unpacked_bits = bch2_bkey_format_current.bits_per_field[i];
 			u64 unpacked_max = ~((~0ULL << 1) << (unpacked_bits - 1));
-			u64 packed_max = f->bits_per_field[i]
-				? ~((~0ULL << 1) << (f->bits_per_field[i] - 1))
+			unsigned bits_per_field = f->bits_per_field[i];
+			if (bits_per_field > bch2_max_bits_per_field[i]) {
+				prt_printf(err, "field %u uses more bits than allowed: %u > %u",
+						i, bits_per_field, bch2_max_bits_per_field[i]);
+				return -BCH_ERR_invalid;
+			}
+			u64 packed_max = bits_per_field
+				? ~((~0ULL << 1) << (bits_per_field - 1))
 				: 0;
 			u64 field_offset = le64_to_cpu(f->field_offset[i]);
 
-- 
2.34.1