{"id":"CVE-2021-47375","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nblktrace: Fix uaf in blk_trace access after removing by sysfs\n\nThere is an use-after-free problem triggered by following process:\n\n      P1(sda)\t\t\t\tP2(sdb)\n\t\t\techo 0 \u003e /sys/block/sdb/trace/enable\n\t\t\t  blk_trace_remove_queue\n\t\t\t    synchronize_rcu\n\t\t\t    blk_trace_free\n\t\t\t      relay_close\nrcu_read_lock\n__blk_add_trace\n  trace_note_tsk\n  (Iterate running_trace_list)\n\t\t\t        relay_close_buf\n\t\t\t\t  relay_destroy_buf\n\t\t\t\t    kfree(buf)\n    trace_note(sdb's bt)\n      relay_reserve\n        buf-\u003eoffset \u003c- nullptr deference (use-after-free) !!!\nrcu_read_unlock\n\n[  502.714379] BUG: kernel NULL pointer dereference, address:\n0000000000000010\n[  502.715260] #PF: supervisor read access in kernel mode\n[  502.715903] #PF: error_code(0x0000) - not-present page\n[  502.716546] PGD 103984067 P4D 103984067 PUD 17592b067 PMD 0\n[  502.717252] Oops: 0000 [#1] SMP\n[  502.720308] RIP: 0010:trace_note.isra.0+0x86/0x360\n[  502.732872] Call Trace:\n[  502.733193]  __blk_add_trace.cold+0x137/0x1a3\n[  502.733734]  blk_add_trace_rq+0x7b/0xd0\n[  502.734207]  blk_add_trace_rq_issue+0x54/0xa0\n[  502.734755]  blk_mq_start_request+0xde/0x1b0\n[  502.735287]  scsi_queue_rq+0x528/0x1140\n...\n[  502.742704]  sg_new_write.isra.0+0x16e/0x3e0\n[  502.747501]  sg_ioctl+0x466/0x1100\n\nReproduce method:\n  ioctl(/dev/sda, BLKTRACESETUP, blk_user_trace_setup[buf_size=127])\n  ioctl(/dev/sda, BLKTRACESTART)\n  ioctl(/dev/sdb, BLKTRACESETUP, blk_user_trace_setup[buf_size=127])\n  ioctl(/dev/sdb, BLKTRACESTART)\n\n  echo 0 \u003e /sys/block/sdb/trace/enable &\n  // Add delay(mdelay/msleep) before kernel enters blk_trace_free()\n\n  ioctl$SG_IO(/dev/sda, SG_IO, ...)\n  // Enters trace_note_tsk() after blk_trace_free() returned\n  // Use mdelay in rcu region rather than msleep(which may schedule out)\n\nRemove blk_trace from running_list before calling blk_trace_free() by\nsysfs if blk_trace is at Blktrace_running state.","modified":"2026-03-15T21:45:12.713698Z","published":"2024-05-21T15:15:23.290Z","related":["SUSE-SU-2024:1979-1","SUSE-SU-2024:1983-1","SUSE-SU-2024:2008-1","SUSE-SU-2024:2010-1","SUSE-SU-2024:2011-1","SUSE-SU-2024:2019-1","SUSE-SU-2024:2183-1","SUSE-SU-2024:2184-1","SUSE-SU-2024:2185-1","SUSE-SU-2024:2189-1","SUSE-SU-2024:2190-1"],"references":[{"type":"FIX","url":"https://git.kernel.org/stable/c/3815fe7371d2411ce164281cef40d9fc7b323dee"},{"type":"FIX","url":"https://git.kernel.org/stable/c/488da313edf3abea7f7733efe011c96b23740ab5"},{"type":"FIX","url":"https://git.kernel.org/stable/c/5afedf670caf30a2b5a52da96eb7eac7dee6a9c9"},{"type":"FIX","url":"https://git.kernel.org/stable/c/677e362ba807f3aafe6f405c07e0b37244da5222"},{"type":"FIX","url":"https://git.kernel.org/stable/c/a5f8e86192612d0183047448d8bbe7918b3f1a26"},{"type":"FIX","url":"https://git.kernel.org/stable/c/d56171d9360c0170c5c5f8f7e2362a2e999eca40"},{"type":"FIX","url":"https://git.kernel.org/stable/c/dacfd5e4d1142bfb3809aab3634a375f6f373269"},{"type":"FIX","url":"https://git.kernel.org/stable/c/ebb8d26d93c3ec3c7576c52a8373a2309423c069"}],"affected":[{"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2021-47375.json","unresolved_ranges":[{"events":[{"introduced":"2.6.30"},{"fixed":"4.4.286"}]},{"events":[{"introduced":"4.5"},{"fixed":"4.9.285"}]},{"events":[{"introduced":"4.10"},{"fixed":"4.14.249"}]},{"events":[{"introduced":"4.15"},{"fixed":"4.19.209"}]},{"events":[{"introduced":"4.20"},{"fixed":"5.4.150"}]},{"events":[{"introduced":"5.5"},{"fixed":"5.10.70"}]},{"events":[{"introduced":"5.11"},{"fixed":"5.14.9"}]},{"events":[{"introduced":"0"},{"last_affected":"5.15-rc1"}]},{"events":[{"introduced":"0"},{"last_affected":"5.15-rc2"}]}]}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N"}]}