Highly exploitable, CVE-2024-26616 poses a critical security risk that could lead to severe breaches.
Status: Analyzed
Last updated: 🕞 12 Dec 2024, 15:31 UTC
Originally published on: 🕕 11 Mar 2024, 18:15 UTC
Time between publication and last update: 275 days
CVSS Release: version 3
nvd@nist.gov
Primary
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CVE-2024-26616: In the Linux kernel, the following vulnerability has been resolved: btrfs: scrub: avoid use-after-free when chunk length is not 64K aligned [BUG] There is a bug report that, on a ext4-converted btrfs, scrub leads to various problems, including: - "unable to find chunk map" errors BTRFS info (device vdb): scrub: started on devid 1 BTRFS critical (device vdb): unable to find chunk map for logical 2214744064 length 4096 BTRFS critical (device vdb): unable to find chunk map for logical 2214744064 length 45056 This would lead to unrepariable errors. - Use-after-free KASAN reports: ================================================================== BUG: KASAN: slab-use-after-free in __blk_rq_map_sg+0x18f/0x7c0 Read of size 8 at addr ffff8881013c9040 by task btrfs/909 CPU: 0 PID: 909 Comm: btrfs Not tainted 6.7.0-x64v3-dbg #11 c50636e9419a8354555555245df535e380563b2b Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 2023.11-2 12/24/2023 Call Trace: <TASK> dump_stack_lvl+0x43/0x60 print_report+0xcf/0x640 kasan_report+0xa6/0xd0 __blk_rq_map_sg+0x18f/0x7c0 virtblk_prep_rq.isra.0+0x215/0x6a0 [virtio_blk 19a65eeee9ae6fcf02edfad39bb9ddee07dcdaff] virtio_queue_rqs+0xc4/0x310 [virtio_blk 19a65eeee9ae6fcf02edfad39bb9ddee07dcdaff] blk_mq_flush_plug_list.part.0+0x780/0x860 __blk_flush_plug+0x1ba/0x220 blk_finish_plug+0x3b/0x60 submit_initial_group_read+0x10a/0x290 [btrfs e57987a360bed82fe8756dcd3e0de5406ccfe965] flush_scrub_stripes+0x38e/0x430 [btrfs e57987a360bed82fe8756dcd3e0de5406ccfe965] scrub_stripe+0x82a/0xae0 [btrfs e57987a360bed82fe8756dcd3e0de5406ccfe965] scrub_chunk+0x178/0x200 [btrfs e57987a360bed82fe8756dcd3e0de5406ccfe965] scrub_enumerate_chunks+0x4bc/0xa30 [btrfs e57987a360bed82fe8756dcd3e0de5406ccfe965] btrfs_scrub_dev+0x398/0x810 [btrfs e57987a360bed82fe8756dcd3e0de5406ccfe965] btrfs_ioctl+0x4b9/0x3020 [btrfs e57987a360bed82fe8756dcd3e0de5406ccfe965] __x64_sys_ioctl+0xbd/0x100 do_syscall_64+0x5d/0xe0 entry_SYSCALL_64_after_hwframe+0x63/0x6b RIP: 0033:0x7f47e5e0952b - Crash, mostly due to above use-after-free [CAUSE] The converted fs has the following data chunk layout: item 2 key (FIRST_CHUNK_TREE CHUNK_ITEM 2214658048) itemoff 16025 itemsize 80 length 86016 owner 2 stripe_len 65536 type DATA|single For above logical bytenr 2214744064, it's at the chunk end (2214658048 + 86016 = 2214744064). This means btrfs_submit_bio() would split the bio, and trigger endio function for both of the two halves. However scrub_submit_initial_read() would only expect the endio function to be called once, not any more. This means the first endio function would already free the bbio::bio, leaving the bvec freed, thus the 2nd endio call would lead to use-after-free. [FIX] - Make sure scrub_read_endio() only updates bits in its range Since we may read less than 64K at the end of the chunk, we should not touch the bits beyond chunk boundary. - Make sure scrub_submit_initial_read() only to read the chunk range This is done by calculating the real number of sectors we need to read, and add sector-by-sector to the bio. Thankfully the scrub read repair path won't need extra fixes: - scrub_stripe_submit_repair_read() With above fixes, we won't update error bit for range beyond chunk, thus scrub_stripe_submit_repair_read() should never submit any read beyond the chunk.
The exploitability of CVE-2024-26616 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-2024-26616 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-2024-26616, 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-2024-26616, 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: 0.042% (probability of exploit)
EPSS Percentile: 5.02%
(lower percentile = lower relative risk)
This vulnerability is less risky than approximately 94.98% of others.
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