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SubjectRe: [PATCH] mm: kmemleak: start address align for scan_large_block
On Wed, Oct 11, 2017 at 04:53:34PM +0800, shuwang@redhat.com wrote:
> From: Shu Wang <shuwang@redhat.com>
>
> If the start address is not ptr bytes aligned, it may cause false
> positives when a pointer is split by MAX_SCAN_SIZE.
>
> For example:
> tcp_metrics_nl_family is in __ro_after_init area. On my PC, the
> __start_ro_after_init is not ptr aligned, and
> tcp_metrics_nl_family->attrbuf was break by MAX_SCAN_SIZE.
>
> # cat /proc/kallsyms | grep __start_ro_after_init
> ffffffff81afac8b R __start_ro_after_init
>
> (gdb) p &tcp_metrics_nl_family->attrbuf
> (struct nlattr ***) 0xffffffff81b12c88 <tcp_metrics_nl_family+72>
>
> (gdb) p tcp_metrics_nl_family->attrbuf
> (struct nlattr **) 0xffff88007b9d9400
>
> scan_block(_start=0xffffffff81b11c8b, _end=0xffffffff81b12c8b, 0)
> scan_block(_start=0xffffffff81b12c8b, _end=0xffffffff81b13c8b, 0)
>
> unreferenced object 0xffff88007b9d9400 (size 128):
> backtrace:
> kmemleak_alloc+0x4a/0xa0
> __kmalloc+0xec/0x220
> genl_register_family.part.8+0x11c/0x5c0
> genl_register_family+0x6f/0x90
> tcp_metrics_init+0x33/0x47
> tcp_init+0x27a/0x293
> inet_init+0x176/0x28a
> do_one_initcall+0x51/0x1b0
>
> Signed-off-by: Shu Wang <shuwang@redhat.com>

Nice catch. Thanks.

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

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