CVE-2022-49898
Here is a potential title for the vulnerability: "Btrfs Linux Kernel Tree Mod Log Mishandling Vulnerability"
Description
In the Linux kernel, the following vulnerability has been resolved: btrfs: fix tree mod log mishandling of reallocated nodes We have been seeing the following panic in production kernel BUG at fs/btrfs/tree-mod-log.c:677! invalid opcode: 0000 [#1] SMP RIP: 0010:tree_mod_log_rewind+0x1b4/0x200 RSP: 0000:ffffc9002c02f890 EFLAGS: 00010293 RAX: 0000000000000003 RBX: ffff8882b448c700 RCX: 0000000000000000 RDX: 0000000000008000 RSI: 00000000000000a7 RDI: ffff88877d831c00 RBP: 0000000000000002 R08: 000000000000009f R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000100c40 R12: 0000000000000001 R13: ffff8886c26d6a00 R14: ffff88829f5424f8 R15: ffff88877d831a00 FS: 00007fee1d80c780(0000) GS:ffff8890400c0000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fee1963a020 CR3: 0000000434f33002 CR4: 00000000007706e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 PKRU: 55555554 Call Trace: btrfs_get_old_root+0x12b/0x420 btrfs_search_old_slot+0x64/0x2f0 ? tree_mod_log_oldest_root+0x3d/0xf0 resolve_indirect_ref+0xfd/0x660 ? ulist_alloc+0x31/0x60 ? kmem_cache_alloc_trace+0x114/0x2c0 find_parent_nodes+0x97a/0x17e0 ? ulist_alloc+0x30/0x60 btrfs_find_all_roots_safe+0x97/0x150 iterate_extent_inodes+0x154/0x370 ? btrfs_search_path_in_tree+0x240/0x240 iterate_inodes_from_logical+0x98/0xd0 ? btrfs_search_path_in_tree+0x240/0x240 btrfs_ioctl_logical_to_ino+0xd9/0x180 btrfs_ioctl+0xe2/0x2ec0 ? __mod_memcg_lruvec_state+0x3d/0x280 ? do_sys_openat2+0x6d/0x140 ? kretprobe_dispatcher+0x47/0x70 ? kretprobe_rethook_handler+0x38/0x50 ? rethook_trampoline_handler+0x82/0x140 ? arch_rethook_trampoline_callback+0x3b/0x50 ? kmem_cache_free+0xfb/0x270 ? do_sys_openat2+0xd5/0x140 __x64_sys_ioctl+0x71/0xb0 do_syscall_64+0x2d/0x40 Which is this code in tree_mod_log_rewind() switch (tm->op) { case BTRFS_MOD_LOG_KEY_REMOVE_WHILE_FREEING: BUG_ON(tm->slot < n); This occurs because we replay the nodes in order that they happened, and when we do a REPLACE we will log a REMOVE_WHILE_FREEING for every slot, starting at 0. 'n' here is the number of items in this block, which in this case was 1, but we had 2 REMOVE_WHILE_FREEING operations. The actual root cause of this was that we were replaying operations for a block that shouldn't have been replayed. Consider the following sequence of events 1. We have an already modified root, and we do a btrfs_get_tree_mod_seq(). 2. We begin removing items from this root, triggering KEY_REPLACE for it's child slots. 3. We remove one of the 2 children this root node points to, thus triggering the root node promotion of the remaining child, and freeing this node. 4. We modify a new root, and re-allocate the above node to the root node of this other root. The tree mod log looks something like this logical 0 op KEY_REPLACE (slot 1) seq 2 logical 0 op KEY_REMOVE (slot 1) seq 3 logical 0 op KEY_REMOVE_WHILE_FREEING (slot 0) seq 4 logical 4096 op LOG_ROOT_REPLACE (old logical 0) seq 5 logical 8192 op KEY_REMOVE_WHILE_FREEING (slot 1) seq 6 logical 8192 op KEY_REMOVE_WHILE_FREEING (slot 0) seq 7 logical 0 op LOG_ROOT_REPLACE (old logical 8192) seq 8 >From here the bug is triggered by the following steps 1. Call btrfs_get_old_root() on the new_root. 2. We call tree_mod_log_oldest_root(btrfs_root_node(new_root)), which is currently logical 0. 3. tree_mod_log_oldest_root() calls tree_mod_log_search_oldest(), which gives us the KEY_REPLACE seq 2, and since that's not a LOG_ROOT_REPLACE we incorrectly believe that we don't have an old root, because we expect that the most recent change should be a LOG_ROOT_REPLACE. 4. Back in tree_mod_log_oldest_root() we don't have a LOG_ROOT_REPLACE, so we don't set old_root, we simply use our e ---truncated---
INFO
Published Date :
May 1, 2025, 3:16 p.m.
Last Modified :
May 2, 2025, 1:52 p.m.
Source :
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Remotely Exploitable :
No
Impact Score :
Exploitability Score :
References to Advisories, Solutions, and Tools
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New CVE Received by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
May. 01, 2025
Action Type Old Value New Value Added Description In the Linux kernel, the following vulnerability has been resolved: btrfs: fix tree mod log mishandling of reallocated nodes We have been seeing the following panic in production kernel BUG at fs/btrfs/tree-mod-log.c:677! invalid opcode: 0000 [#1] SMP RIP: 0010:tree_mod_log_rewind+0x1b4/0x200 RSP: 0000:ffffc9002c02f890 EFLAGS: 00010293 RAX: 0000000000000003 RBX: ffff8882b448c700 RCX: 0000000000000000 RDX: 0000000000008000 RSI: 00000000000000a7 RDI: ffff88877d831c00 RBP: 0000000000000002 R08: 000000000000009f R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000100c40 R12: 0000000000000001 R13: ffff8886c26d6a00 R14: ffff88829f5424f8 R15: ffff88877d831a00 FS: 00007fee1d80c780(0000) GS:ffff8890400c0000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fee1963a020 CR3: 0000000434f33002 CR4: 00000000007706e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 PKRU: 55555554 Call Trace: btrfs_get_old_root+0x12b/0x420 btrfs_search_old_slot+0x64/0x2f0 ? tree_mod_log_oldest_root+0x3d/0xf0 resolve_indirect_ref+0xfd/0x660 ? ulist_alloc+0x31/0x60 ? kmem_cache_alloc_trace+0x114/0x2c0 find_parent_nodes+0x97a/0x17e0 ? ulist_alloc+0x30/0x60 btrfs_find_all_roots_safe+0x97/0x150 iterate_extent_inodes+0x154/0x370 ? btrfs_search_path_in_tree+0x240/0x240 iterate_inodes_from_logical+0x98/0xd0 ? btrfs_search_path_in_tree+0x240/0x240 btrfs_ioctl_logical_to_ino+0xd9/0x180 btrfs_ioctl+0xe2/0x2ec0 ? __mod_memcg_lruvec_state+0x3d/0x280 ? do_sys_openat2+0x6d/0x140 ? kretprobe_dispatcher+0x47/0x70 ? kretprobe_rethook_handler+0x38/0x50 ? rethook_trampoline_handler+0x82/0x140 ? arch_rethook_trampoline_callback+0x3b/0x50 ? kmem_cache_free+0xfb/0x270 ? do_sys_openat2+0xd5/0x140 __x64_sys_ioctl+0x71/0xb0 do_syscall_64+0x2d/0x40 Which is this code in tree_mod_log_rewind() switch (tm->op) { case BTRFS_MOD_LOG_KEY_REMOVE_WHILE_FREEING: BUG_ON(tm->slot < n); This occurs because we replay the nodes in order that they happened, and when we do a REPLACE we will log a REMOVE_WHILE_FREEING for every slot, starting at 0. 'n' here is the number of items in this block, which in this case was 1, but we had 2 REMOVE_WHILE_FREEING operations. The actual root cause of this was that we were replaying operations for a block that shouldn't have been replayed. Consider the following sequence of events 1. We have an already modified root, and we do a btrfs_get_tree_mod_seq(). 2. We begin removing items from this root, triggering KEY_REPLACE for it's child slots. 3. We remove one of the 2 children this root node points to, thus triggering the root node promotion of the remaining child, and freeing this node. 4. We modify a new root, and re-allocate the above node to the root node of this other root. The tree mod log looks something like this logical 0 op KEY_REPLACE (slot 1) seq 2 logical 0 op KEY_REMOVE (slot 1) seq 3 logical 0 op KEY_REMOVE_WHILE_FREEING (slot 0) seq 4 logical 4096 op LOG_ROOT_REPLACE (old logical 0) seq 5 logical 8192 op KEY_REMOVE_WHILE_FREEING (slot 1) seq 6 logical 8192 op KEY_REMOVE_WHILE_FREEING (slot 0) seq 7 logical 0 op LOG_ROOT_REPLACE (old logical 8192) seq 8 >From here the bug is triggered by the following steps 1. Call btrfs_get_old_root() on the new_root. 2. We call tree_mod_log_oldest_root(btrfs_root_node(new_root)), which is currently logical 0. 3. tree_mod_log_oldest_root() calls tree_mod_log_search_oldest(), which gives us the KEY_REPLACE seq 2, and since that's not a LOG_ROOT_REPLACE we incorrectly believe that we don't have an old root, because we expect that the most recent change should be a LOG_ROOT_REPLACE. 4. Back in tree_mod_log_oldest_root() we don't have a LOG_ROOT_REPLACE, so we don't set old_root, we simply use our e ---truncated--- Added Reference https://git.kernel.org/stable/c/007058eb8292efc4c88f921752194b83269da085 Added Reference https://git.kernel.org/stable/c/52b2b65c9eb56fd829dda323786db828627ff7e6 Added Reference https://git.kernel.org/stable/c/968b71583130b6104c9f33ba60446d598e327a8b
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2022-49898 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2022-49898
weaknesses.