| From bippy-5f407fcff5a0 Mon Sep 17 00:00:00 2001 |
| From: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| To: <linux-cve-announce@vger.kernel.org> |
| Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org> |
| Subject: CVE-2024-49885: mm, slub: avoid zeroing kmalloc redzone |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| mm, slub: avoid zeroing kmalloc redzone |
| |
| Since commit 946fa0dbf2d8 ("mm/slub: extend redzone check to extra |
| allocated kmalloc space than requested"), setting orig_size treats |
| the wasted space (object_size - orig_size) as a redzone. However with |
| init_on_free=1 we clear the full object->size, including the redzone. |
| |
| Additionally we clear the object metadata, including the stored orig_size, |
| making it zero, which makes check_object() treat the whole object as a |
| redzone. |
| |
| These issues lead to the following BUG report with "slub_debug=FUZ |
| init_on_free=1": |
| |
| [ 0.000000] ============================================================================= |
| [ 0.000000] BUG kmalloc-8 (Not tainted): kmalloc Redzone overwritten |
| [ 0.000000] ----------------------------------------------------------------------------- |
| [ 0.000000] |
| [ 0.000000] 0xffff000010032858-0xffff00001003285f @offset=2136. First byte 0x0 instead of 0xcc |
| [ 0.000000] FIX kmalloc-8: Restoring kmalloc Redzone 0xffff000010032858-0xffff00001003285f=0xcc |
| [ 0.000000] Slab 0xfffffdffc0400c80 objects=36 used=23 fp=0xffff000010032a18 flags=0x3fffe0000000200(workingset|node=0|zone=0|lastcpupid=0x1ffff) |
| [ 0.000000] Object 0xffff000010032858 @offset=2136 fp=0xffff0000100328c8 |
| [ 0.000000] |
| [ 0.000000] Redzone ffff000010032850: cc cc cc cc cc cc cc cc ........ |
| [ 0.000000] Object ffff000010032858: cc cc cc cc cc cc cc cc ........ |
| [ 0.000000] Redzone ffff000010032860: cc cc cc cc cc cc cc cc ........ |
| [ 0.000000] Padding ffff0000100328b4: 00 00 00 00 00 00 00 00 00 00 00 00 ............ |
| [ 0.000000] CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted 6.11.0-rc3-next-20240814-00004-g61844c55c3f4 #144 |
| [ 0.000000] Hardware name: NXP i.MX95 19X19 board (DT) |
| [ 0.000000] Call trace: |
| [ 0.000000] dump_backtrace+0x90/0xe8 |
| [ 0.000000] show_stack+0x18/0x24 |
| [ 0.000000] dump_stack_lvl+0x74/0x8c |
| [ 0.000000] dump_stack+0x18/0x24 |
| [ 0.000000] print_trailer+0x150/0x218 |
| [ 0.000000] check_object+0xe4/0x454 |
| [ 0.000000] free_to_partial_list+0x2f8/0x5ec |
| |
| To address the issue, use orig_size to clear the used area. And restore |
| the value of orig_size after clear the remaining area. |
| |
| When CONFIG_SLUB_DEBUG not defined, (get_orig_size()' directly returns |
| s->object_size. So when using memset to init the area, the size can simply |
| be orig_size, as orig_size returns object_size when CONFIG_SLUB_DEBUG not |
| enabled. And orig_size can never be bigger than object_size. |
| |
| The Linux kernel CVE team has assigned CVE-2024-49885 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 6.2 with commit 946fa0dbf2d8923a587f7348adf16563d59f1b3d and fixed in 6.10.14 with commit 7a2e823a19746d54052c625faecf0d2d6c52ee0a |
| Issue introduced in 6.2 with commit 946fa0dbf2d8923a587f7348adf16563d59f1b3d and fixed in 6.11.3 with commit 83f0440b2f92227fcce9898118ca7fe7e0d64b1f |
| Issue introduced in 6.2 with commit 946fa0dbf2d8923a587f7348adf16563d59f1b3d and fixed in 6.12 with commit 59090e479ac78ae18facd4c58eb332562a23020e |
| |
| Please see https://www.kernel.org for a full list of currently supported |
| kernel versions by the kernel community. |
| |
| Unaffected versions might change over time as fixes are backported to |
| older supported kernel versions. The official CVE entry at |
| https://cve.org/CVERecord/?id=CVE-2024-49885 |
| will be updated if fixes are backported, please check that for the most |
| up to date information about this issue. |
| |
| |
| Affected files |
| ============== |
| |
| The file(s) affected by this issue are: |
| mm/slub.c |
| |
| |
| Mitigation |
| ========== |
| |
| The Linux kernel CVE team recommends that you update to the latest |
| stable kernel version for this, and many other bugfixes. Individual |
| changes are never tested alone, but rather are part of a larger kernel |
| release. Cherry-picking individual commits is not recommended or |
| supported by the Linux kernel community at all. If however, updating to |
| the latest release is impossible, the individual changes to resolve this |
| issue can be found at these commits: |
| https://git.kernel.org/stable/c/7a2e823a19746d54052c625faecf0d2d6c52ee0a |
| https://git.kernel.org/stable/c/83f0440b2f92227fcce9898118ca7fe7e0d64b1f |
| https://git.kernel.org/stable/c/59090e479ac78ae18facd4c58eb332562a23020e |
