Re: [PATCH] mm/kmemleak: Reset tag when compare object pointer

[Catalin Marinas]

On Fri, Mar 18, 2022 at 11:40:48AM +0800, Kuan-Ying Lee wrote:
> When we use HW-tag based kasan and enable vmalloc support, we hit
> the following bug. It is due to comparison between tagged object
> and non-tagged pointer.
> 
> We need to reset the kasan tag when we need to compare tagged object
> and non-tagged pointer.
> 
> [    7.690429][T400001] init: kmemleak: [name:kmemleak&]Scan area larger than object 0xffffffe77076f440
> [    7.691762][T400001] init: CPU: 4 PID: 1 Comm: init Tainted: G S      W         5.15.25-android13-0-g5cacf919c2bc #1
> [    7.693218][T400001] init: Hardware name: MT6983(ENG) (DT)
> [    7.693983][T400001] init: Call trace:
> [    7.694508][T400001] init:  dump_backtrace.cfi_jt+0x0/0x8
> [    7.695272][T400001] init:  dump_stack_lvl+0xac/0x120
> [    7.695985][T400001] init:  add_scan_area+0xc4/0x244
> [    7.696685][T400001] init:  kmemleak_scan_area+0x40/0x9c
> [    7.697428][T400001] init:  layout_and_allocate+0x1e8/0x288
> [    7.698211][T400001] init:  load_module+0x2c8/0xf00
> [    7.698895][T400001] init:  __se_sys_finit_module+0x190/0x1d0
> [    7.699701][T400001] init:  __arm64_sys_finit_module+0x20/0x30
> [    7.700517][T400001] init:  invoke_syscall+0x60/0x170
> [    7.701225][T400001] init:  el0_svc_common+0xc8/0x114
> [    7.701933][T400001] init:  do_el0_svc+0x28/0xa0
> [    7.702580][T400001] init:  el0_svc+0x60/0xf8
> [    7.703196][T400001] init:  el0t_64_sync_handler+0x88/0xec
> [    7.703964][T400001] init:  el0t_64_sync+0x1b4/0x1b8
> [    7.704658][T400001] init: kmemleak: [name:kmemleak&]Object 0xf5ffffe77076b000 (size 32768):
> [    7.705824][T400001] init: kmemleak: [name:kmemleak&]  comm "init", pid 1, jiffies 4294894197
> [    7.707002][T400001] init: kmemleak: [name:kmemleak&]  min_count = 0
> [    7.707886][T400001] init: kmemleak: [name:kmemleak&]  count = 0
> [    7.708718][T400001] init: kmemleak: [name:kmemleak&]  flags = 0x1
> [    7.709574][T400001] init: kmemleak: [name:kmemleak&]  checksum = 0
> [    7.710440][T400001] init: kmemleak: [name:kmemleak&]  backtrace:
> [    7.711284][T400001] init:      module_alloc+0x9c/0x120
> [    7.712015][T400001] init:      move_module+0x34/0x19c
> [    7.712735][T400001] init:      layout_and_allocate+0x1c4/0x288
> [    7.713561][T400001] init:      load_module+0x2c8/0xf00
> [    7.714291][T400001] init:      __se_sys_finit_module+0x190/0x1d0
> [    7.715142][T400001] init:      __arm64_sys_finit_module+0x20/0x30
> [    7.716004][T400001] init:      invoke_syscall+0x60/0x170
> [    7.716758][T400001] init:      el0_svc_common+0xc8/0x114
> [    7.717512][T400001] init:      do_el0_svc+0x28/0xa0
> [    7.718207][T400001] init:      el0_svc+0x60/0xf8
> [    7.718869][T400001] init:      el0t_64_sync_handler+0x88/0xec
> [    7.719683][T400001] init:      el0t_64_sync+0x1b4/0x1b8
> 
> Signed-off-by: Kuan-Ying Lee <Kuan-Ying.Lee@xxxxxxxxxxxx>

Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx>