On Fri, 25 Oct 2024, Qun-Wei Lin wrote: > 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 > ================================================================== > > Fixes: 1a83a716ec233 ("mm: krealloc: consider spare memory for > __GFP_ZERO") > Signed-off-by: Qun-Wei Lin <qun-wei.lin@xxxxxxxxxxxx> Acked-by: David Rientjes <rientjes@xxxxxxxxxx>