{"id":"CVE-2026-45990","summary":"slub: fix data loss and overflow in krealloc()","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nslub: fix data loss and overflow in krealloc()\n\nCommit 2cd8231796b5 (\"mm/slub: allow to set node and align in\nk[v]realloc\") introduced the ability to force a reallocation if the\noriginal object does not satisfy new alignment or NUMA node, even when\nthe object is being shrunk.\n\nThis introduced two bugs in the reallocation fallback path:\n\n1. Data loss during NUMA migration: The jump to 'alloc_new' happens\n   before 'ks' and 'orig_size' are initialized. As a result, the\n   memcpy() in the 'alloc_new' block would copy 0 bytes into the new\n   allocation.\n\n2. Buffer overflow during shrinking: When shrinking an object while\n   forcing a new alignment, 'new_size' is smaller than the old size.\n   However, the memcpy() used the old size ('orig_size ?: ks'), leading\n   to an out-of-bounds write.\n\nThe same overflow bug exists in the kvrealloc() fallback path, where the\nold bucket size ksize(p) is copied into the new buffer without being\nbounded by the new size.\n\nA simple reproducer:\n\n\t// e.g. add to lkdtm as KREALLOC_SHRINK_OVERFLOW\n\twhile (1) {\n\t\tvoid *p = kmalloc(128, GFP_KERNEL);\n\t\tp = krealloc_node_align(p, 64, 256, GFP_KERNEL, NUMA_NO_NODE);\n\t\tkfree(p);\n\t}\n\ndemonstrates the issue:\n\n  ==================================================================\n  BUG: KFENCE: out-of-bounds write in memcpy_orig+0x68/0x130\n\n  Out-of-bounds write at 0xffff8883ad757038 (120B right of kfence-#47):\n   memcpy_orig+0x68/0x130\n   krealloc_node_align_noprof+0x1c8/0x340\n   lkdtm_KREALLOC_SHRINK_OVERFLOW+0x8c/0xc0 [lkdtm]\n   lkdtm_do_action+0x3a/0x60 [lkdtm]\n   ...\n\n  kfence-#47: 0xffff8883ad756fc0-0xffff8883ad756fff, size=64, cache=kmalloc-64\n\n  allocated by task 316 on cpu 7 at 97.680481s (0.021813s ago):\n   krealloc_node_align_noprof+0x19c/0x340\n   lkdtm_KREALLOC_SHRINK_OVERFLOW+0x8c/0xc0 [lkdtm]\n   lkdtm_do_action+0x3a/0x60 [lkdtm]\n   ...\n  ==================================================================\n\nFix it by moving the old size calculation to the top of __do_krealloc()\nand bounding all copy lengths by the new allocation size.","modified":"2026-06-18T03:54:48.835064296Z","published":"2026-05-27T12:55:42.572Z","related":["openSUSE-SU-2026:10954-1"],"database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/45xxx/CVE-2026-45990.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/082a6d03a2d685a83a332666b500ad3966349588"},{"type":"WEB","url":"https://git.kernel.org/stable/c/38387ccc0fbe38d14fb4c2ad7ee1d7404e5e59fd"},{"type":"WEB","url":"https://git.kernel.org/stable/c/550fa6b5aabb096554536ac1e3ec96b76cbb35fd"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/45xxx/CVE-2026-45990.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-45990"},{"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":"2cd8231796b5e7133b1c3d66ad7d2a3c42c97258"},{"fixed":"38387ccc0fbe38d14fb4c2ad7ee1d7404e5e59fd"},{"fixed":"550fa6b5aabb096554536ac1e3ec96b76cbb35fd"},{"fixed":"082a6d03a2d685a83a332666b500ad3966349588"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-45990.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"6.18.0"},{"fixed":"6.18.27"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.0.4"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-45990.json"}}],"schema_version":"1.7.5"}