CVE-2021-47375
blktrace: Fix uaf in blk_trace access after removing by sysfs
- Published
- Updated
- Reserved
- Assigned by
- Linux
Description
In the Linux kernel, the following vulnerability has been resolved: blktrace: Fix uaf in blk_trace access after removing by sysfs There is an use-after-free problem triggered by following process: P1(sda) P2(sdb) echo 0 > /sys/block/sdb/trace/enable blk_trace_remove_queue synchronize_rcu blk_trace_free relay_close rcu_read_lock __blk_add_trace trace_note_tsk (Iterate running_trace_list) relay_close_buf relay_destroy_buf kfree(buf) trace_note(sdb's bt) relay_reserve buf->offset <- nullptr deference (use-after-free) !!! rcu_read_unlock [ 502.714379] BUG: kernel NULL pointer dereference, address: 0000000000000010 [ 502.715260] #PF: supervisor read access in kernel mode [ 502.715903] #PF: error_code(0x0000) - not-present page [ 502.716546] PGD 103984067 P4D 103984067 PUD 17592b067 PMD 0 [ 502.717252] Oops: 0000 [#1] SMP [ 502.720308] RIP: 0010:trace_note.isra.0+0x86/0x360 [ 502.732872] Call Trace: [ 502.733193] __blk_add_trace.cold+0x137/0x1a3 [ 502.733734] blk_add_trace_rq+0x7b/0xd0 [ 502.734207] blk_add_trace_rq_issue+0x54/0xa0 [ 502.734755] blk_mq_start_request+0xde/0x1b0 [ 502.735287] scsi_queue_rq+0x528/0x1140 ... [ 502.742704] sg_new_write.isra.0+0x16e/0x3e0 [ 502.747501] sg_ioctl+0x466/0x1100 Reproduce method: ioctl(/dev/sda, BLKTRACESETUP, blk_user_trace_setup[buf_size=127]) ioctl(/dev/sda, BLKTRACESTART) ioctl(/dev/sdb, BLKTRACESETUP, blk_user_trace_setup[buf_size=127]) ioctl(/dev/sdb, BLKTRACESTART) echo 0 > /sys/block/sdb/trace/enable & // Add delay(mdelay/msleep) before kernel enters blk_trace_free() ioctl$SG_IO(/dev/sda, SG_IO, ...) // Enters trace_note_tsk() after blk_trace_free() returned // Use mdelay in rcu region rather than msleep(which may schedule out) Remove blk_trace from running_list before calling blk_trace_free() by sysfs if blk_trace is at Blktrace_running state.
Timeline
ID reserved
By Linux
Published
- 24 months later
· 24 months later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| CISA-ADPADP (enrichment) | 3.1 | Medium6.2 | CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N |
| NVDNVD · Analyzed | 3.1 | Medium6.2 | CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N |
- EPSS (exploitation in 30 days)
- 0.25% · top 83% of all CVEs (7 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 6.2.
Weakness
Affected products
- affected c71a896154119f4ca9e89d6078f5f63ad60ef199 – < 488da313edf3abea7f7733efe011c96b23740ab5
- affected c71a896154119f4ca9e89d6078f5f63ad60ef199 – < dacfd5e4d1142bfb3809aab3634a375f6f373269
- affected c71a896154119f4ca9e89d6078f5f63ad60ef199 – < d56171d9360c0170c5c5f8f7e2362a2e999eca40
- affected c71a896154119f4ca9e89d6078f5f63ad60ef199 – < 677e362ba807f3aafe6f405c07e0b37244da5222
- affected c71a896154119f4ca9e89d6078f5f63ad60ef199 – < ebb8d26d93c3ec3c7576c52a8373a2309423c069
- affected c71a896154119f4ca9e89d6078f5f63ad60ef199 – < 3815fe7371d2411ce164281cef40d9fc7b323dee
- affected c71a896154119f4ca9e89d6078f5f63ad60ef199 – < a5f8e86192612d0183047448d8bbe7918b3f1a26
- affected c71a896154119f4ca9e89d6078f5f63ad60ef199 – < 5afedf670caf30a2b5a52da96eb7eac7dee6a9c9
- affected 2.6.30
- unaffected < 2.6.30
- unaffected 4.4.286 – ≤ 4.4.*
- unaffected 4.9.285 – ≤ 4.9.*
- unaffected 4.14.249 – ≤ 4.14.*
- unaffected 4.19.209 – ≤ 4.19.*
- unaffected 5.4.150 – ≤ 5.4.*
- unaffected 5.10.70 – ≤ 5.10.*
- unaffected 5.14.9 – ≤ 5.14.*
- unaffected 5.15 – ≤ *
References (8)
- https://git.kernel.org/stable/c/488da313edf3abea7f7733efe011c96b23740ab5 (opens in a new tab)x_transferred
- https://git.kernel.org/stable/c/dacfd5e4d1142bfb3809aab3634a375f6f373269 (opens in a new tab)x_transferred
- https://git.kernel.org/stable/c/d56171d9360c0170c5c5f8f7e2362a2e999eca40 (opens in a new tab)x_transferred
- https://git.kernel.org/stable/c/677e362ba807f3aafe6f405c07e0b37244da5222 (opens in a new tab)x_transferred
- https://git.kernel.org/stable/c/ebb8d26d93c3ec3c7576c52a8373a2309423c069 (opens in a new tab)x_transferred
- https://git.kernel.org/stable/c/3815fe7371d2411ce164281cef40d9fc7b323dee (opens in a new tab)x_transferred
- https://git.kernel.org/stable/c/a5f8e86192612d0183047448d8bbe7918b3f1a26 (opens in a new tab)x_transferred
- https://git.kernel.org/stable/c/5afedf670caf30a2b5a52da96eb7eac7dee6a9c9 (opens in a new tab)x_transferred
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
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[](https://trackcve.app/cve/CVE-2021-47375)Record last updated .