| Message ID | 20241025085811.31310-1-qun-wei.lin@mediatek.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm: krealloc: Fix MTE false alarm in __do_krealloc | expand |
On 10/25/24 10:58, 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@mediatek.com> Thanks, added to slab hotfixes for 6.12 > --- > mm/slab_common.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/slab_common.c b/mm/slab_common.c > index 3d26c257ed8b..3445f4500b54 100644 > --- a/mm/slab_common.c > +++ b/mm/slab_common.c > @@ -1209,7 +1209,7 @@ __do_krealloc(const void *p, size_t new_size, gfp_t flags) > /* 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((void *)p + new_size), 0, ks - new_size); > kasan_enable_current(); > } >
diff --git a/mm/slab_common.c b/mm/slab_common.c index 3d26c257ed8b..3445f4500b54 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -1209,7 +1209,7 @@ __do_krealloc(const void *p, size_t new_size, gfp_t flags) /* 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((void *)p + new_size), 0, ks - new_size); kasan_enable_current(); }
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> --- mm/slab_common.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)