slub: fix data loss and overflow in krealloc()
Summary
| CVE | CVE-2026-45990 |
|---|---|
| State | PUBLISHED |
| Assigner | Linux |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-05-27 14:17:16 UTC |
| Updated | 2026-05-27 14:48:03 UTC |
| Description | In the Linux kernel, the following vulnerability has been resolved: slub: fix data loss and overflow in krealloc() Commit 2cd8231796b5 ("mm/slub: allow to set node and align in k[v]realloc") introduced the ability to force a reallocation if the original object does not satisfy new alignment or NUMA node, even when the object is being shrunk. This introduced two bugs in the reallocation fallback path: 1. Data loss during NUMA migration: The jump to 'alloc_new' happens before 'ks' and 'orig_size' are initialized. As a result, the memcpy() in the 'alloc_new' block would copy 0 bytes into the new allocation. 2. Buffer overflow during shrinking: When shrinking an object while forcing a new alignment, 'new_size' is smaller than the old size. However, the memcpy() used the old size ('orig_size ?: ks'), leading to an out-of-bounds write. The same overflow bug exists in the kvrealloc() fallback path, where the old bucket size ksize(p) is copied into the new buffer without being bounded by the new size. A simple reproducer: // e.g. add to lkdtm as KREALLOC_SHRINK_OVERFLOW while (1) { void *p = kmalloc(128, GFP_KERNEL); p = krealloc_node_align(p, 64, 256, GFP_KERNEL, NUMA_NO_NODE); kfree(p); } demonstrates the issue: ================================================================== BUG: KFENCE: out-of-bounds write in memcpy_orig+0x68/0x130 Out-of-bounds write at 0xffff8883ad757038 (120B right of kfence-#47): memcpy_orig+0x68/0x130 krealloc_node_align_noprof+0x1c8/0x340 lkdtm_KREALLOC_SHRINK_OVERFLOW+0x8c/0xc0 [lkdtm] lkdtm_do_action+0x3a/0x60 [lkdtm] ... kfence-#47: 0xffff8883ad756fc0-0xffff8883ad756fff, size=64, cache=kmalloc-64 allocated by task 316 on cpu 7 at 97.680481s (0.021813s ago): krealloc_node_align_noprof+0x19c/0x340 lkdtm_KREALLOC_SHRINK_OVERFLOW+0x8c/0xc0 [lkdtm] lkdtm_do_action+0x3a/0x60 [lkdtm] ... ================================================================== Fix it by moving the old size calculation to the top of __do_krealloc() and bounding all copy lengths by the new allocation size. |
Risk And Classification
EPSS: 0.000170000 probability, percentile 0.043220000 (date 2026-05-28)
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Linux | Linux | affected 2cd8231796b5e7133b1c3d66ad7d2a3c42c97258 38387ccc0fbe38d14fb4c2ad7ee1d7404e5e59fd git | Not specified |
| CNA | Linux | Linux | affected 2cd8231796b5e7133b1c3d66ad7d2a3c42c97258 550fa6b5aabb096554536ac1e3ec96b76cbb35fd git | Not specified |
| CNA | Linux | Linux | affected 2cd8231796b5e7133b1c3d66ad7d2a3c42c97258 082a6d03a2d685a83a332666b500ad3966349588 git | Not specified |
| CNA | Linux | Linux | affected 6.18 | Not specified |
| CNA | Linux | Linux | unaffected 6.18 semver | Not specified |
| CNA | Linux | Linux | unaffected 6.18.27 6.18.* semver | Not specified |
| CNA | Linux | Linux | unaffected 7.0.4 7.0.* semver | Not specified |
| CNA | Linux | Linux | unaffected 7.1-rc1 * original_commit_for_fix | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| git.kernel.org/stable/c/082a6d03a2d685a83a332666b500ad3966349588 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/38387ccc0fbe38d14fb4c2ad7ee1d7404e5e59fd | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/550fa6b5aabb096554536ac1e3ec96b76cbb35fd | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
No vendor comments have been submitted for this CVE.
There are currently no legacy QID mappings associated with this CVE.