6.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Qu Wenruo wqu@suse.com
[ Upstream commit 724d8042cef84496ddb4492dc120291f997ae26b ]
[BUG] Syzbot reports the following regression detected by KASAN:
BUG: KASAN: slab-out-of-bounds in btrfs_qgroup_inherit+0x42e/0x2e20 fs/btrfs/qgroup.c:3277 Read of size 8 at addr ffff88814628ca50 by task syz-executor318/5171
CPU: 0 PID: 5171 Comm: syz-executor318 Not tainted 6.10.0-rc2-syzkaller-00010-g2ab795141095 #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 print_address_description mm/kasan/report.c:377 [inline] print_report+0x169/0x550 mm/kasan/report.c:488 kasan_report+0x143/0x180 mm/kasan/report.c:601 btrfs_qgroup_inherit+0x42e/0x2e20 fs/btrfs/qgroup.c:3277 create_pending_snapshot+0x1359/0x29b0 fs/btrfs/transaction.c:1854 create_pending_snapshots+0x195/0x1d0 fs/btrfs/transaction.c:1922 btrfs_commit_transaction+0xf20/0x3740 fs/btrfs/transaction.c:2382 create_snapshot+0x6a1/0x9e0 fs/btrfs/ioctl.c:875 btrfs_mksubvol+0x58f/0x710 fs/btrfs/ioctl.c:1029 btrfs_mksnapshot+0xb5/0xf0 fs/btrfs/ioctl.c:1075 __btrfs_ioctl_snap_create+0x387/0x4b0 fs/btrfs/ioctl.c:1340 btrfs_ioctl_snap_create_v2+0x1f2/0x3a0 fs/btrfs/ioctl.c:1422 btrfs_ioctl+0x99e/0xc60 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:907 [inline] __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:893 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fcbf1992509 RSP: 002b:00007fcbf1928218 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007fcbf1a1f618 RCX: 00007fcbf1992509 RDX: 0000000020000280 RSI: 0000000050009417 RDI: 0000000000000003 RBP: 00007fcbf1a1f610 R08: 00007ffea1298e97 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007fcbf19eb660 R13: 00000000200002b8 R14: 00007fcbf19e60c0 R15: 0030656c69662f2e </TASK>
And it also pinned it down to commit b5357cb268c4 ("btrfs: qgroup: do not check qgroup inherit if qgroup is disabled").
[CAUSE] That offending commit skips the whole qgroup inherit check if qgroup is not enabled.
But that also skips the very basic checks like num_ref_copies/num_excl_copies and the structure size checks.
Meaning if a qgroup enable/disable race is happening at the background, and we pass a btrfs_qgroup_inherit structure when the qgroup is disabled, the check would be completely skipped.
Then at the time of transaction commitment, qgroup is re-enabled and btrfs_qgroup_inherit() is going to use the incorrect structure and causing the above KASAN error.
[FIX] Make btrfs_qgroup_check_inherit() only skip the source qgroup checks. So that even if invalid btrfs_qgroup_inherit structure is passed in, we can still reject invalid ones no matter if qgroup is enabled or not.
Furthermore we do already have an extra safety inside btrfs_qgroup_inherit(), which would just ignore invalid qgroup sources, so even if we only skip the qgroup source check we're still safe.
Reported-by: syzbot+a0d1f7e26910be4dc171@syzkaller.appspotmail.com Fixes: b5357cb268c4 ("btrfs: qgroup: do not check qgroup inherit if qgroup is disabled") Reviewed-by: Boris Burkov boris@bur.io Reviewed-by: Jeongjun Park aha310510@gmail.com Signed-off-by: Qu Wenruo wqu@suse.com Reviewed-by: David Sterba dsterba@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/btrfs/qgroup.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c index 1167899a16d05..4caa078d972a3 100644 --- a/fs/btrfs/qgroup.c +++ b/fs/btrfs/qgroup.c @@ -3065,8 +3065,6 @@ int btrfs_qgroup_check_inherit(struct btrfs_fs_info *fs_info, struct btrfs_qgroup_inherit *inherit, size_t size) { - if (!btrfs_qgroup_enabled(fs_info)) - return 0; if (inherit->flags & ~BTRFS_QGROUP_INHERIT_FLAGS_SUPP) return -EOPNOTSUPP; if (size < sizeof(*inherit) || size > PAGE_SIZE) @@ -3090,6 +3088,14 @@ int btrfs_qgroup_check_inherit(struct btrfs_fs_info *fs_info, if (size != struct_size(inherit, qgroups, inherit->num_qgroups)) return -EINVAL;
+ /* + * Skip the inherit source qgroups check if qgroup is not enabled. + * Qgroup can still be later enabled causing problems, but in that case + * btrfs_qgroup_inherit() would just ignore those invalid ones. + */ + if (!btrfs_qgroup_enabled(fs_info)) + return 0; + /* * Now check all the remaining qgroups, they should all: *