CVE-2024-50118
Vulnerability Scoring
Security assessments indicate that CVE-2024-50118 presents a notable risk, potentially requiring prompt mitigation.
Security assessments indicate that CVE-2024-50118 presents a notable risk, potentially requiring prompt mitigation.
Status: Analyzed
Last updated: 🕕 08 Nov 2024, 18:02 UTC
Originally published on: 🕕 05 Nov 2024, 18:15 UTC
Time between publication and last update: 2 days
CVSS Release: version 3
nvd@nist.gov
Primary
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
CVE-2024-50118: In the Linux kernel, the following vulnerability has been resolved: btrfs: reject ro->rw reconfiguration if there are hard ro requirements [BUG] Syzbot reports the following crash: BTRFS info (device loop0 state MCS): disabling free space tree BTRFS info (device loop0 state MCS): clearing compat-ro feature flag for FREE_SPACE_TREE (0x1) BTRFS info (device loop0 state MCS): clearing compat-ro feature flag for FREE_SPACE_TREE_VALID (0x2) Oops: general protection fault, probably for non-canonical address 0xdffffc0000000003: 0000 [#1] PREEMPT SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x0000000000000018-0x000000000000001f] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 RIP: 0010:backup_super_roots fs/btrfs/disk-io.c:1691 [inline] RIP: 0010:write_all_supers+0x97a/0x40f0 fs/btrfs/disk-io.c:4041 Call Trace: <TASK> btrfs_commit_transaction+0x1eae/0x3740 fs/btrfs/transaction.c:2530 btrfs_delete_free_space_tree+0x383/0x730 fs/btrfs/free-space-tree.c:1312 btrfs_start_pre_rw_mount+0xf28/0x1300 fs/btrfs/disk-io.c:3012 btrfs_remount_rw fs/btrfs/super.c:1309 [inline] btrfs_reconfigure+0xae6/0x2d40 fs/btrfs/super.c:1534 btrfs_reconfigure_for_mount fs/btrfs/super.c:2020 [inline] btrfs_get_tree_subvol fs/btrfs/super.c:2079 [inline] btrfs_get_tree+0x918/0x1920 fs/btrfs/super.c:2115 vfs_get_tree+0x90/0x2b0 fs/super.c:1800 do_new_mount+0x2be/0xb40 fs/namespace.c:3472 do_mount fs/namespace.c:3812 [inline] __do_sys_mount fs/namespace.c:4020 [inline] __se_sys_mount+0x2d6/0x3c0 fs/namespace.c:3997 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 [CAUSE] To support mounting different subvolume with different RO/RW flags for the new mount APIs, btrfs introduced two workaround to support this feature: - Skip mount option/feature checks if we are mounting a different subvolume - Reconfigure the fs to RW if the initial mount is RO Combining these two, we can have the following sequence: - Mount the fs ro,rescue=all,clear_cache,space_cache=v1 rescue=all will mark the fs as hard read-only, so no v2 cache clearing will happen. - Mount a subvolume rw of the same fs. We go into btrfs_get_tree_subvol(), but fc_mount() returns EBUSY because our new fc is RW, different from the original fs. Now we enter btrfs_reconfigure_for_mount(), which switches the RO flag first so that we can grab the existing fs_info. Then we reconfigure the fs to RW. - During reconfiguration, option/features check is skipped This means we will restart the v2 cache clearing, and convert back to v1 cache. This will trigger fs writes, and since the original fs has "rescue=all" option, it skips the csum tree read. And eventually causing NULL pointer dereference in super block writeback. [FIX] For reconfiguration caused by different subvolume RO/RW flags, ensure we always run btrfs_check_options() to ensure we have proper hard RO requirements met. In fact the function btrfs_check_options() doesn't really do many complex checks, but hard RO requirement and some feature dependency checks, thus there is no special reason not to do the check for mount reconfiguration.
The exploitability of CVE-2024-50118 depends on two key factors: attack complexity (the level of effort required to execute an exploit) and privileges required (the access level an attacker needs).
CVE-2024-50118 presents an accessible attack vector with minimal effort required. Restricting access controls and implementing security updates are critical to reducing exploitation risks.
A lower complexity and fewer privilege requirements make exploitation easier. Security teams should evaluate these aspects to determine the urgency of mitigation strategies, such as patch management and access control policies.
Attack Complexity (AC) measures the difficulty in executing an exploit. A high AC means that specific conditions must be met, making an attack more challenging, while a low AC means the vulnerability can be exploited with minimal effort.
Privileges Required (PR) determine the level of system access necessary for an attack. Vulnerabilities requiring no privileges are more accessible to attackers, whereas high privilege requirements limit exploitation to authorized users with elevated access.
Above is the CVSS Sub-score Breakdown for CVE-2024-50118, illustrating how Base, Impact, and Exploitability factors combine to form the overall severity rating. A higher sub-score typically indicates a more severe or easier-to-exploit vulnerability.
Below is the Impact Analysis for CVE-2024-50118, showing how Confidentiality, Integrity, and Availability might be affected if the vulnerability is exploited. Higher values usually signal greater potential damage.
The EPSS score estimates the probability that this vulnerability will be exploited in the near future.
EPSS Score: 0.043% (probability of exploit)
EPSS Percentile: 11.87%
(lower percentile = lower relative risk)
This vulnerability is less risky than approximately 88.13% of others.
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