{"id":"CVE-2026-74261","summary":"ALSA: seq: avoid stale FIFO cells during resize","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nALSA: seq: avoid stale FIFO cells during resize\n\nsnd_seq_fifo_resize() still needs to publish the replacement pool\nbefore it waits for FIFO users. A blocking snd_seq_read() holds\nf-\u003euse_lock while it sleeps, so concurrent senders must be able to\nqueue to the new pool and wake that reader instead of failing against a\nclosing old pool.\n\nHowever, snd_seq_fifo_event_in() duplicates an event before it takes\nf-\u003elock, and snd_seq_read() can dequeue a cell and later call\nsnd_seq_fifo_cell_putback() if copy_to_user() or\nsnd_seq_expand_var_event() fails. If resize swaps f-\u003epool and detaches\noldhead in between, either path can relink an old-pool cell after the\nsnapshot. That stale cell sits outside the drained oldhead list, keeps\noldpool-\u003ecounter elevated, and can leave snd_seq_pool_delete() waiting\nfor the retired pool to drain.\n\nKeep the existing swap-before-wait ordering in snd_seq_fifo_resize(),\nbut reject stale cells before any FIFO relink. Revalidate event-in cells\nunder f-\u003elock and retry them against the published replacement pool, and\nfree stale putback cells instead of linking them back into the FIFO.\n\nThe buggy scenario involves two paths, with each column showing the\norder within that path:\n\nresize path:                    relink path:\n1. Allocate newpool.             1. Take f-\u003euse_lock.\n2. Swap f-\u003epool to newpool and   2. Duplicate or dequeue an old-pool\n   detach oldhead.                  cell before oldpool closes.\n3. Mark oldpool closing and      3. Reach a later relink point after\n   wait for FIFO users.             resize published newpool.\n4. Free oldhead and delete       4. Relink the old-pool cell after\n   oldpool.                         resize detached oldhead.\n                                 5. Drop f-\u003euse_lock.\n\nThe reproducer reports a resize ioctl blocked in the expected pool\nteardown path:\n\nsignal: resize iteration=98 target_pool=4 exceeded 250ms\n        (elapsed=251ms)\ndiagnostic: resize_tid=651 wchan=snd_seq_pool_done\ndiagnostic: resize_tid=651 stack=\n  snd_seq_pool_done+0x5b/0x140\n  snd_seq_pool_delete+0x7a/0x90\n  snd_seq_fifo_resize+0x193/0x1e0\n  snd_seq_ioctl_set_client_pool+0x214/0x260\n  snd_seq_ioctl+0x119/0x540\n  __x64_sys_ioctl+0xd1/0x120\n  do_syscall_64+0xbb/0x2f0\n  entry_SYSCALL_64_after_hwframe+0x77/0x7f\n\nA second run with larger pools hit the same target path:\n\nsignal: resize iteration=32 target_pool=64 exceeded 250ms\n        (elapsed=251ms)\ndiagnostic: resize_tid=663 wchan=snd_seq_pool_done\ndiagnostic: resize_tid=663 stack=\n  snd_seq_pool_done+0x5b/0x140\n  snd_seq_pool_delete+0x7a/0x90\n  snd_seq_fifo_resize+0x193/0x1e0\n  snd_seq_ioctl_set_client_pool+0x214/0x260\n  snd_seq_ioctl+0x119/0x540\n  __x64_sys_ioctl+0xd1/0x120\n  do_syscall_64+0xbb/0x2f0\n  entry_SYSCALL_64_after_hwframe+0x77/0x7f","modified":"2026-11-01T02:30:50.461349912Z","published":"2026-08-15T05:57:38.311Z","related":["SUSE-SU-2026:23881-1","SUSE-SU-2026:23887-1","SUSE-SU-2026:23897-1","SUSE-SU-2026:23902-1","SUSE-SU-2026:24181-1","SUSE-SU-2026:24182-1","SUSE-SU-2026:24315-1","SUSE-SU-2026:24316-1","SUSE-SU-2026:4282-1","SUSE-SU-2026:4640-1","SUSE-SU-2026:4706-1","openSUSE-SU-2026:21910-1"],"database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/74xxx/CVE-2026-74261.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/1c4c35fb68d520241f7d9f1c356b5e2370fd8364"},{"type":"WEB","url":"https://git.kernel.org/stable/c/8bb506ffb848e3de1496a4cf23a2fd694da2a7d2"},{"type":"WEB","url":"https://git.kernel.org/stable/c/98a965cb1e767b54b6bbd831b6cea26f521a8f51"},{"type":"WEB","url":"https://git.kernel.org/stable/c/ae429220c7f9747579bc4682c574585230e971cc"},{"type":"WEB","url":"https://git.kernel.org/stable/c/dcf784abee6df2f5c47e36a1d9e400065993bc04"},{"type":"WEB","url":"https://git.kernel.org/stable/c/e546128291f8d688dcb931827e2efd2aa6c0734d"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/74xxx/CVE-2026-74261.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-74261"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"2d7d54002e396c180db0c800c1046f0a3c471597"},{"fixed":"8bb506ffb848e3de1496a4cf23a2fd694da2a7d2"},{"fixed":"ae429220c7f9747579bc4682c574585230e971cc"},{"fixed":"dcf784abee6df2f5c47e36a1d9e400065993bc04"},{"fixed":"98a965cb1e767b54b6bbd831b6cea26f521a8f51"},{"fixed":"1c4c35fb68d520241f7d9f1c356b5e2370fd8364"},{"fixed":"e546128291f8d688dcb931827e2efd2aa6c0734d"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"3.2.91"},{"fixed":"3.3"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"3.10.107"},{"fixed":"3.11"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"3.12.73"},{"fixed":"3.13"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"3.16.46"},{"fixed":"3.17"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"3.18.50"},{"fixed":"3.19"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"4.1.40"},{"fixed":"4.2"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"4.4.60"},{"fixed":"4.5"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"4.9.21"},{"fixed":"4.10"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"4.10.9"},{"fixed":"4.11"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"df7a2d0af9f7ab73cf22a7b62bbc0bad93a02110"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"28e0ebdd57cd3287ac821068364b74c70af3861c"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"d4b8e8a32d74052fe292618ae19f794944ddc673"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"e91325f27c4d98d1088e9e86b3ab475f752eeb80"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"9ebfed203c0d93449a074c5c2fd5bb3e58518f0d"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"3492352e1f34673708fa7409b4b1d97545aa2f1c"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"a90d7447e4a154ad26e3b9e09a0878680be49339"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"74a2c1ff88a4e0960623d17f7db56ac5a60bb0cf"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"c36ef6467420f8982e6d4d6f93d0634a85a5ee45"}]}],"versions":["v3.2.102","v3.2.101","v3.2.100","v3.2.99","v3.2.98","v3.2.97","v3.2.96","v3.2.95","v3.2.94","v3.2.93","v3.2.92","v3.2.91","v3.10.108","v3.10.107","v3.12.74","v3.12.73","v3.16.85","v3.16.84","v3.16.83","v3.16.82","v3.16.81","v3.16.80","v3.16.79","v3.16.78","v3.16.77","v3.16.76","v3.16.75","v3.16.74","v3.16.73","v3.16.72","v3.16.71","v3.16.70","v3.16.69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