From: Guo Xuenan <guoxuenan@xxxxxxxxxx> Source kernel commit: 0cb227895e6f8369c1a2b9110e291a35223b8de1 For leaf dir, In most cases, there should be as many bestfree slots as the dir data blocks that can fit under i_size (except for [1]). Root cause is we don't examin the number bestfree slots, when the slots number less than dir data blocks, if we need to allocate new dir data block and update the bestfree array, we will use the dir block number as index to assign bestfree array, while we did not check the leaf buf boundary which may cause UAF or other memory access problem. This issue can also triggered with test cases xfs/473 from fstests. According to Dave Chinner & Darrick's suggestion, adding buffer verifier to detect this abnormal situation in time. Simplify the testcase for fstest xfs/554 [1] The error log is shown as follows: ================================================================== BUG: KASAN: use-after-free in xfs_dir2_leaf_addname+0x1995/0x1ac0 Write of size 2 at addr ffff88810168b000 by task touch/1552 CPU: 5 PID: 1552 Comm: touch Not tainted 6.0.0-rc3+ #101 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014 Call Trace: <TASK> dump_stack_lvl+0x4d/0x66 print_report.cold+0xf6/0x691 kasan_report+0xa8/0x120 xfs_dir2_leaf_addname+0x1995/0x1ac0 xfs_dir_createname+0x58c/0x7f0 xfs_create+0x7af/0x1010 xfs_generic_create+0x270/0x5e0 path_openat+0x270b/0x3450 do_filp_open+0x1cf/0x2b0 do_sys_openat2+0x46b/0x7a0 do_sys_open+0xb7/0x130 do_syscall_64+0x35/0x80 entry_SYSCALL_64_after_hwframe+0x63/0xcd RIP: 0033:0x7fe4d9e9312b Code: 25 00 00 41 00 3d 00 00 41 00 74 4b 64 8b 04 25 18 00 00 00 85 c0 75 67 44 89 e2 48 89 ee bf 9c ff ff ff b8 01 01 00 00 0f 05 <48> 3d 00 f0 ff ff 0f 87 91 00 00 00 48 8b 4c 24 28 64 48 33 0c 25 RSP: 002b:00007ffda4c16c20 EFLAGS: 00000246 ORIG_RAX: 0000000000000101 RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007fe4d9e9312b RDX: 0000000000000941 RSI: 00007ffda4c17f33 RDI: 00000000ffffff9c RBP: 00007ffda4c17f33 R08: 0000000000000000 R09: 0000000000000000 R10: 00000000000001b6 R11: 0000000000000246 R12: 0000000000000941 R13: 00007fe4d9f631a4 R14: 00007ffda4c17f33 R15: 0000000000000000 </TASK> The buggy address belongs to the physical page: page:ffffea000405a2c0 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10168b flags: 0x2fffff80000000(node=0|zone=2|lastcpupid=0x1fffff) raw: 002fffff80000000 ffffea0004057788 ffffea000402dbc8 0000000000000000 raw: 0000000000000000 0000000000170000 00000000ffffffff 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff88810168af00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffff88810168af80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 >ffff88810168b000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ^ ffff88810168b080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ffff88810168b100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ================================================================== Disabling lock debugging due to kernel taint 00000000: 58 44 44 33 5b 53 35 c2 00 00 00 00 00 00 00 78 XDD3[S5........x XFS (sdb): Internal error xfs_dir2_data_use_free at line 1200 of file fs/xfs/libxfs/xfs_dir2_data.c. Caller xfs_dir2_data_use_free+0x28a/0xeb0 CPU: 5 PID: 1552 Comm: touch Tainted: G B 6.0.0-rc3+ Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014 Call Trace: <TASK> dump_stack_lvl+0x4d/0x66 xfs_corruption_error+0x132/0x150 xfs_dir2_data_use_free+0x198/0xeb0 xfs_dir2_leaf_addname+0xa59/0x1ac0 xfs_dir_createname+0x58c/0x7f0 xfs_create+0x7af/0x1010 xfs_generic_create+0x270/0x5e0 path_openat+0x270b/0x3450 do_filp_open+0x1cf/0x2b0 do_sys_openat2+0x46b/0x7a0 do_sys_open+0xb7/0x130 do_syscall_64+0x35/0x80 entry_SYSCALL_64_after_hwframe+0x63/0xcd RIP: 0033:0x7fe4d9e9312b Code: 25 00 00 41 00 3d 00 00 41 00 74 4b 64 8b 04 25 18 00 00 00 85 c0 75 67 44 89 e2 48 89 ee bf 9c ff ff ff b8 01 01 00 00 0f 05 <48> 3d 00 f0 ff ff 0f 87 91 00 00 00 48 8b 4c 24 28 64 48 33 0c 25 RSP: 002b:00007ffda4c16c20 EFLAGS: 00000246 ORIG_RAX: 0000000000000101 RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007fe4d9e9312b RDX: 0000000000000941 RSI: 00007ffda4c17f46 RDI: 00000000ffffff9c RBP: 00007ffda4c17f46 R08: 0000000000000000 R09: 0000000000000001 R10: 00000000000001b6 R11: 0000000000000246 R12: 0000000000000941 R13: 00007fe4d9f631a4 R14: 00007ffda4c17f46 R15: 0000000000000000 </TASK> XFS (sdb): Corruption detected. Unmount and run xfs_repair [1] https://lore.kernel.org/all/20220928095355.2074025-1-guoxuenan@xxxxxxxxxx/ Reviewed-by: Hou Tao <houtao1@xxxxxxxxxx> Signed-off-by: Guo Xuenan <guoxuenan@xxxxxxxxxx> Reviewed-by: Darrick J. Wong <djwong@xxxxxxxxxx> Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx> --- libxfs/xfs_dir2_leaf.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/libxfs/xfs_dir2_leaf.c b/libxfs/xfs_dir2_leaf.c index 8827c96c18..5da66006cb 100644 --- a/libxfs/xfs_dir2_leaf.c +++ b/libxfs/xfs_dir2_leaf.c @@ -144,6 +144,8 @@ xfs_dir3_leaf_check_int( xfs_dir2_leaf_tail_t *ltp; int stale; int i; + bool isleaf1 = (hdr->magic == XFS_DIR2_LEAF1_MAGIC || + hdr->magic == XFS_DIR3_LEAF1_MAGIC); ltp = xfs_dir2_leaf_tail_p(geo, leaf); @@ -156,8 +158,7 @@ xfs_dir3_leaf_check_int( return __this_address; /* Leaves and bests don't overlap in leaf format. */ - if ((hdr->magic == XFS_DIR2_LEAF1_MAGIC || - hdr->magic == XFS_DIR3_LEAF1_MAGIC) && + if (isleaf1 && (char *)&hdr->ents[hdr->count] > (char *)xfs_dir2_leaf_bests_p(ltp)) return __this_address; @@ -173,6 +174,10 @@ xfs_dir3_leaf_check_int( } if (hdr->ents[i].address == cpu_to_be32(XFS_DIR2_NULL_DATAPTR)) stale++; + if (isleaf1 && xfs_dir2_dataptr_to_db(geo, + be32_to_cpu(hdr->ents[i].address)) >= + be32_to_cpu(ltp->bestcount)) + return __this_address; } if (hdr->stale != stale) return __this_address;
