6.6-stable review patch. If anyone has any objections, please let me know.
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From: Qun-Wei Lin qun-wei.lin@mediatek.com
commit 704573851b51808b45dae2d62059d1d8189138a2 upstream.
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@mediatek.com Acked-by: David Rientjes rientjes@google.com Signed-off-by: Vlastimil Babka vbabka@suse.cz Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/slab_common.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -1391,7 +1391,7 @@ __do_krealloc(const void *p, size_t new_ /* Zero out spare memory. */ if (want_init_on_alloc(flags)) { kasan_disable_current(); - memset((void *)p + new_size, 0, ks - new_size); + memset(kasan_reset_tag(p) + new_size, 0, ks - new_size); kasan_enable_current(); }