# CVE-2024-46789: linux: In the Linux kernel, the following vulnerability has been resolved:  mm/slub: add check for s->flags in the alloc_tag...

CVE-2024-46789 is fixed in linux on 1 platform, first by DEBIAN-CVE-2024-46789, released September 18, 2024. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2024-46789
- Priority: Routine
- CVSS: 5.5 (medium)
- EPSS: 0.0018
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 18, 2024

## Description

In the Linux kernel, the following vulnerability has been resolved:  mm/slub: add check for s->flags in the alloc_tagging_slab_free_hook  When enable CONFIG_MEMCG & CONFIG_KFENCE & CONFIG_KMEMLEAK, the following warning always occurs,This is because the following call stack occurred: mem_pool_alloc     kmem_cache_alloc_noprof         slab_alloc_node             kfence_alloc  Once the kfence allocation is successful,slab->obj_exts will not be empty, because it has already been assigned a value in kfence_init_pool.  Since in the prepare_slab_obj_exts_hook function,we perform a check for s->flags & (SLAB_NO_OBJ_EXT | SLAB_NOLEAKTRACE),the alloc_tag_add function will not be called as a result.Therefore,ref->ct remains NULL.  However,when we call mem_pool_free,since obj_ext is not empty, it eventually leads to the alloc_tag_sub scenario being invoked.  This is where the warning occurs.  So we should add corresponding checks in the alloc_tagging_slab_free_hook. For __GFP_NO_OBJ_EXT case,I didn't see the specific case where it's using kfence,so I won't add the corresponding check in alloc_tagging_slab_free_hook for now.  [    3.734349] ------------[ cut here ]------------ [    3.734807] alloc_tag was not set [    3.735129] WARNING: CPU: 4 PID: 40 at ./include/linux/alloc_tag.h:130 kmem_cache_free+0x444/0x574 [    3.735866] Modules linked in: autofs4 [    3.736211] CPU: 4 UID: 0 PID: 40 Comm: ksoftirqd/4 Tainted: G        W          6.11.0-rc3-dirty #1 [    3.736969] Tainted: [W]=WARN [    3.737258] Hardware name: QEMU KVM Virtual Machine, BIOS unknown 2/2/2022 [    3.737875] pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) [    3.738501] pc : kmem_cache_free+0x444/0x574 [    3.738951] lr : kmem_cache_free+0x444/0x574 [    3.739361] sp : ffff80008357bb60 [    3.739693] x29: ffff80008357bb70 x28: 0000000000000000 x27: 0000000000000000 [    3.740338] x26: ffff80008207f000 x25: ffff000b2eb2fd60 x24: ffff0000c0005700 [    3.740982] x23: ffff8000804229e4 x22: ffff800082080000 x21: ffff800081756000 [    3.741630] x20: fffffd7ff8253360 x19: 00000000000000a8 x18: ffffffffffffffff [    3.742274] x17: ffff800ab327f000 x16: ffff800083398000 x15: ffff800081756df0 [    3.742919] x14: 0000000000000000 x13: 205d344320202020 x12: 5b5d373038343337 [    3.743560] x11: ffff80008357b650 x10: 000000000000005d x9 : 00000000ffffffd0 [    3.744231] x8 : 7f7f7f7f7f7f7f7f x7 : ffff80008237bad0 x6 : c0000000ffff7fff [    3.744907] x5 : ffff80008237ba78 x4 : ffff8000820bbad0 x3 : 0000000000000001 [    3.745580] x2 : 68d66547c09f7800 x1 : 68d66547c09f7800 x0 : 0000000000000000 [    3.746255] Call trace: [    3.746530]  kmem_cache_free+0x444/0x574 [    3.746931]  mem_pool_free+0x44/0xf4 [    3.747306]  free_object_rcu+0xc8/0xdc [    3.747693]  rcu_do_batch+0x234/0x8a4 [    3.748075]  rcu_core+0x230/0x3e4 [    3.748424]  rcu_core_si+0x14/0x1c [    3.748780]  handle_softirqs+0x134/0x378 [    3.749189]  run_ksoftirqd+0x70/0x9c [    3.749560]  smpboot_thread_fn+0x148/0x22c [    3.749978]  kthread+0x10c/0x118 [    3.750323]  ret_from_fork+0x10/0x20 [    3.750696] ---[ end trace 0000000000000000 ]---

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 13.5 (trixie) | 6.10.11-1 | [DEBIAN-CVE-2024-46789](https://patchblox.com/security/data/fix/linux/debian-cve-2024-46789.md) | Sep 18, 2024 |
| Linux | linux Debian 14 | 6.10.11-1 | [DEBIAN-CVE-2024-46789](https://patchblox.com/security/data/fix/linux/debian-cve-2024-46789.md) | Sep 18, 2024 |

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