{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2024-56592", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2024-12-27T14:03:06.003Z", "datePublished": "2024-12-27T14:50:59.673Z", "dateUpdated": "2026-05-11T20:55:26.485Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-05-11T20:55:26.485Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Call free_htab_elem() after htab_unlock_bucket()\n\nFor htab of maps, when the map is removed from the htab, it may hold the\nlast reference of the map. bpf_map_fd_put_ptr() will invoke\nbpf_map_free_id() to free the id of the removed map element. However,\nbpf_map_fd_put_ptr() is invoked while holding a bucket lock\n(raw_spin_lock_t), and bpf_map_free_id() attempts to acquire map_idr_lock\n(spinlock_t), triggering the following lockdep warning:\n\n =============================\n [ BUG: Invalid wait context ]\n 6.11.0-rc4+ #49 Not tainted\n -----------------------------\n test_maps/4881 is trying to lock:\n ffffffff84884578 (map_idr_lock){+...}-{3:3}, at: bpf_map_free_id.part.0+0x21/0x70\n other info that might help us debug this:\n context-{5:5}\n 2 locks held by test_maps/4881:\n #0: ffffffff846caf60 (rcu_read_lock){....}-{1:3}, at: bpf_fd_htab_map_update_elem+0xf9/0x270\n #1: ffff888149ced148 (&htab->lockdep_key#2){....}-{2:2}, at: htab_map_update_elem+0x178/0xa80\n stack backtrace:\n CPU: 0 UID: 0 PID: 4881 Comm: test_maps Not tainted 6.11.0-rc4+ #49\n Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), ...\n Call Trace:\n \n dump_stack_lvl+0x6e/0xb0\n dump_stack+0x10/0x20\n __lock_acquire+0x73e/0x36c0\n lock_acquire+0x182/0x450\n _raw_spin_lock_irqsave+0x43/0x70\n bpf_map_free_id.part.0+0x21/0x70\n bpf_map_put+0xcf/0x110\n bpf_map_fd_put_ptr+0x9a/0xb0\n free_htab_elem+0x69/0xe0\n htab_map_update_elem+0x50f/0xa80\n bpf_fd_htab_map_update_elem+0x131/0x270\n htab_map_update_elem+0x50f/0xa80\n bpf_fd_htab_map_update_elem+0x131/0x270\n bpf_map_update_value+0x266/0x380\n __sys_bpf+0x21bb/0x36b0\n __x64_sys_bpf+0x45/0x60\n x64_sys_call+0x1b2a/0x20d0\n do_syscall_64+0x5d/0x100\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\n\nOne way to fix the lockdep warning is using raw_spinlock_t for\nmap_idr_lock as well. However, bpf_map_alloc_id() invokes\nidr_alloc_cyclic() after acquiring map_idr_lock, it will trigger a\nsimilar lockdep warning because the slab's lock (s->cpu_slab->lock) is\nstill a spinlock.\n\nInstead of changing map_idr_lock's type, fix the issue by invoking\nhtab_put_fd_value() after htab_unlock_bucket(). However, only deferring\nthe invocation of htab_put_fd_value() is not enough, because the old map\npointers in htab of maps can not be saved during batched deletion.\nTherefore, also defer the invocation of free_htab_elem(), so these\nto-be-freed elements could be linked together similar to lru map.\n\nThere are four callers for ->map_fd_put_ptr:\n\n(1) alloc_htab_elem() (through htab_put_fd_value())\nIt invokes ->map_fd_put_ptr() under a raw_spinlock_t. The invocation of\nhtab_put_fd_value() can not simply move after htab_unlock_bucket(),\nbecause the old element has already been stashed in htab->extra_elems.\nIt may be reused immediately after htab_unlock_bucket() and the\ninvocation of htab_put_fd_value() after htab_unlock_bucket() may release\nthe newly-added element incorrectly. Therefore, saving the map pointer\nof the old element for htab of maps before unlocking the bucket and\nreleasing the map_ptr after unlock. Beside the map pointer in the old\nelement, should do the same thing for the special fields in the old\nelement as well.\n\n(2) free_htab_elem() (through htab_put_fd_value())\nIts caller includes __htab_map_lookup_and_delete_elem(),\nhtab_map_delete_elem() and __htab_map_lookup_and_delete_batch().\n\nFor htab_map_delete_elem(), simply invoke free_htab_elem() after\nhtab_unlock_bucket(). For __htab_map_lookup_and_delete_batch(), just\nlike lru map, linking the to-be-freed element into node_to_free list\nand invoking free_htab_elem() for these element after unlock. It is safe\nto reuse batch_flink as the link for node_to_free, because these\nelements have been removed from the hash llist.\n\nBecause htab of maps doesn't support lookup_and_delete operation,\n__htab_map_lookup_and_delete_elem() doesn't have the problem, so kept\nit as\n---truncated---" } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "kernel/bpf/hashtab.c" ], "versions": [ { "version": "f3f1c054c288bb6e503005e6d73611151ed20e91", "lessThan": "10e8a2dec9ff1b81de8e892b0850924038adbc6d", "status": "affected", "versionType": "git" }, { "version": "f3f1c054c288bb6e503005e6d73611151ed20e91", "lessThan": "a50b4aa3007e63a590d501341f304676ebc74b3b", "status": "affected", "versionType": "git" }, { "version": "f3f1c054c288bb6e503005e6d73611151ed20e91", "lessThan": "b9e9ed90b10c82a4e9d4d70a2890f06bfcdd3b78", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "kernel/bpf/hashtab.c" ], "versions": [ { "version": "4.13", "status": "affected" }, { "version": "0", "lessThan": "4.13", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.66", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.5", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.13", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.13", "versionEndExcluding": "6.6.66" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.13", "versionEndExcluding": "6.12.5" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.13", "versionEndExcluding": "6.13" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/10e8a2dec9ff1b81de8e892b0850924038adbc6d" }, { "url": "https://git.kernel.org/stable/c/a50b4aa3007e63a590d501341f304676ebc74b3b" }, { "url": "https://git.kernel.org/stable/c/b9e9ed90b10c82a4e9d4d70a2890f06bfcdd3b78" } ], "title": "bpf: Call free_htab_elem() after htab_unlock_bucket()", "x_generator": { "engine": "bippy-1.2.0" } } } }