Messages in this thread Patch in this message | | | From | shuwang@redhat ... | Subject | [PATCH] mm: kmemleak: start address align for scan_large_block | Date | Wed, 11 Oct 2017 16:53:34 +0800 |
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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> --- mm/kmemleak.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/mm/kmemleak.c b/mm/kmemleak.c index 7780cd83a495..388b73e01fa4 100644 --- a/mm/kmemleak.c +++ b/mm/kmemleak.c @@ -1376,6 +1376,7 @@ static void scan_block(void *_start, void *_end, static void scan_large_block(void *start, void *end) { void *next; + start = PTR_ALIGN(start, BYTES_PER_POINTER); while (start < end) { next = min(start + MAX_SCAN_SIZE, end); -- 2.13.5
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