[syzbot] [bcachefs?] UBSAN: shift-out-of-bounds in bch2_sb_dev_has_data

[syzbot] [bcachefs?] UBSAN: shift-out-of-bounds in bch2_sb_dev_has_data

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    cf87f46fd34d Merge tag 'drm-fixes-2024-05-11' of https://g..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=162f8fbc980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=9d7ea7de0cb32587
dashboard link: https://syzkaller.appspot.com/bug?extid=249018ea545364f78d04
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=13a40d04980000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=102e5b70980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/9c147953fc8e/disk-cf87f46f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a55c9d1f91fc/vmlinux-cf87f46f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f8dab47ae8c2/bzImage-cf87f46f.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/2c5c030a256e/mount_0.gz

The issue was bisected to:

commit 03ef80b469d5d83530ce1ce15be78a40e5300f9b
Author: Kent Overstreet <kent.overstreet@linux.dev>
Date:   Sat Sep 23 22:41:51 2023 +0000

    bcachefs: Ignore unknown mount options

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=13d673d4980000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=103673d4980000
console output: https://syzkaller.appspot.com/x/log.txt?x=17d673d4980000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+249018ea545364f78d04@syzkaller.appspotmail.com
Fixes: 03ef80b469d5 ("bcachefs: Ignore unknown mount options")

loop0: detected capacity change from 0 to 32768
------------[ cut here ]------------
UBSAN: shift-out-of-bounds in fs/bcachefs/replicas.c:1010:20
shift exponent 155 is too large for 32-bit type 'int'
CPU: 0 PID: 5075 Comm: syz-executor397 Not tainted 6.9.0-rc7-syzkaller-00183-gcf87f46fd34d #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
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_sb_dev_has_data+0x22a/0x5f0 fs/bcachefs/replicas.c:1010
 member_to_text+0xcb/0x1030 fs/bcachefs/sb-members.c:163
 bch2_sb_members_v1_to_text+0x1aa/0x2f0 fs/bcachefs/sb-members.c:317
 bch2_sb_field_validate+0x1f7/0x2d0 fs/bcachefs/super-io.c:1228
 bch2_sb_validate+0x9b6/0xe10 fs/bcachefs/super-io.c:460
 __bch2_read_super+0xc9a/0x1460 fs/bcachefs/super-io.c:822
 bch2_fs_open+0x246/0xdf0 fs/bcachefs/super.c:2052
 bch2_mount+0x71d/0x1320 fs/bcachefs/fs.c:1903
 legacy_get_tree+0xee/0x190 fs/fs_context.c:662
 vfs_get_tree+0x90/0x2a0 fs/super.c:1779
 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: 0033:0x7f16b990d8ba
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:00007ffdd930ef68 EFLAGS: 00000282 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007ffdd930ef80 RCX: 00007f16b990d8ba
RDX: 0000000020011a00 RSI: 0000000020011a40 RDI: 00007ffdd930ef80
RBP: 0000000000000004 R08: 00007ffdd930efc0 R09: 00000000000119f3
R10: 0000000001200014 R11: 0000000000000282 R12: 0000000001200014
R13: 00007ffdd930efc0 R14: 0000000000000003 R15: 0000000001000000
 </TASK>
---[ end trace ]---


---
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For information about bisection process see: https://goo.gl/tpsmEJ#bisection

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
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#syz undup

Re: [syzbot] [PATCH] guard against unknown r->data_type in bch2_sb_dev_has_data()

[syzbot]

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

***

Subject: [PATCH] guard against unknown r->data_type in bch2_sb_dev_has_data()
Author: cam.alvarez.i@gmail.com

#syz test
Shift is perfomed only when the data type makes sense.

Fix a missing guard on r->data_type being known.

Signed-off-by: Camila Alvarez <cam.alvarez.i@gmail.com>
---
 fs/bcachefs/replicas.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/bcachefs/replicas.c b/fs/bcachefs/replicas.c
index 678b9c20e251..0fa91d0bf951 100644
--- a/fs/bcachefs/replicas.c
+++ b/fs/bcachefs/replicas.c
@@ -1006,14 +1006,14 @@ unsigned bch2_sb_dev_has_data(struct bch_sb *sb, unsigned dev)
 
 		for_each_replicas_entry(replicas, r)
 			for (i = 0; i < r->nr_devs; i++)
-				if (r->devs[i] == dev)
+				if (r->devs[i] == dev && r->data_type < BCH_DATA_NR)
 					data_has |= 1 << r->data_type;
 	} else if (replicas_v0) {
 		struct bch_replicas_entry_v0 *r;
 
 		for_each_replicas_entry_v0(replicas_v0, r)
 			for (i = 0; i < r->nr_devs; i++)
-				if (r->devs[i] == dev)
+				if (r->devs[i] == dev && r->data_type < BCH_DATA_NR)
 					data_has |= 1 << r->data_type;
 	}
 
-- 
2.34.1

Re: [syzbot] [bcachefs?] UBSAN: shift-out-of-bounds in bch2_sb_dev_has_data

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+249018ea545364f78d04@syzkaller.appspotmail.com

Tested on:

commit:         b47c1823 Merge tag 'fsverity-for-linus' of git://git.k..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=143d3084980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=81bc9f1b05e6fe63
dashboard link: https://syzkaller.appspot.com/bug?extid=249018ea545364f78d04
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=134cb5b8980000

Note: testing is done by a robot and is best-effort only.

Re: [syzbot] [bcachefs?] UBSAN: shift-out-of-bounds in bch2_sb_dev_has_data

[Kent Overstreet]

#syz fix: bcachefs: Fix shift overflows in replicas.c