In the Linux kernel, the following vulnerability has been resolved:

mm: krealloc: Fix MTE false alarm in __do_krealloc

This patch addresses an issue introduced by commit 1a83a716ec233 (mm: krealloc: consider spare memory for __GFP_ZERO) which causes MTE (Memory Tagging Extension) to falsely report a slab-out-of-bounds error.

The problem occurs when zeroing out spare memory in __do_krealloc. The original code only considered software-based KASAN and did not account for MTE. It does not reset the KASAN tag before calling memset, leading to a mismatch between the pointer tag and the memory tag, resulting in a false positive.

Example of the error:

swapper/0: BUG: KASAN: slab-out-of-bounds in __memset+0x84/0x188 swapper/0: Write at addr f4ffff8005f0fdf0 by task swapper/0/1 swapper/0: Pointer tag: [f4], memory tag: [fe] swapper/0: swapper/0: CPU: 4 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.12. swapper/0: Hardware name: MT6991(ENG) (DT) swapper/0: Call trace: swapper/0: dump_backtrace+0xfc/0x17c swapper/0: show_stack+0x18/0x28 swapper/0: dump_stack_lvl+0x40/0xa0 swapper/0: print_report+0x1b8/0x71c swapper/0: kasan_report+0xec/0x14c swapper/0: __do_kernel_fault+0x60/0x29c swapper/0: do_bad_area+0x30/0xdc swapper/0: do_tag_check_fault+0x20/0x34 swapper/0: do_mem_abort+0x58/0x104 swapper/0: el1_abort+0x3c/0x5c swapper/0: el1h_64_sync_handler+0x80/0xcc swapper/0: el1h_64_sync+0x68/0x6c swapper/0: __memset+0x84/0x188 swapper/0: btf_populate_kfunc_set+0x280/0x3d8 swapper/0: __register_btf_kfunc_id_set+0x43c/0x468 swapper/0: register_btf_kfunc_id_set+0x48/0x60 swapper/0: register_nf_nat_bpf+0x1c/0x40 swapper/0: nf_nat_init+0xc0/0x128 swapper/0: do_one_initcall+0x184/0x464 swapper/0: do_initcall_level+0xdc/0x1b0 swapper/0: do_initcalls+0x70/0xc0 swapper/0: do_basic_setup+0x1c/0x28 swapper/0: kernel_init_freeable+0x144/0x1b8 swapper/0: kernel_init+0x20/0x1a8 swapper/0: ret_from_fork+0x10/0x20

Affected Software

References

• https://git.kernel.org/stable/c/3dfb40da84f26dd35dd9bbaf626a2424565b8406
• https://git.kernel.org/stable/c/486aeb5f1855c75dd810c25036134961bd2a6722
• https://git.kernel.org/stable/c/704573851b51808b45dae2d62059d1d8189138a2
• https://git.kernel.org/stable/c/71548fada7ee0eb50cc6ccda82dff010c745f92c
• https://git.kernel.org/stable/c/8ebee7565effdeae6085458f8f8463363120a871
• https://git.kernel.org/stable/c/d02492863023431c31f85d570f718433c22b9311
• https://git.kernel.org/stable/c/d43f1430d47c22a0727c05b6f156ed25fecdfeb4