On 4/4/21 4:17 PM, Sergei Trofimovich wrote:
> When page_poison detects page corruption it's useful to see who
> freed a page recently to have a guess where write-after-free
> corruption happens.
>
> After this change corruption report has extra page_owner data.
> Example report from real corruption:
>
> pagealloc: memory corruption
> e00000014cd61d10: 11 00 00 00 00 00 00 00 30 1d d2 ff ff 0f 00 60
> e00000014cd61d20: b0 1d d2 ff ff 0f 00 60 90 fe 1c 00 08 00 00 20
> ...
> CPU: 1 PID: 220402 Comm: cc1plus Not tainted 5.12.0-rc5-00107-g9720c6f59ecf #245
> Hardware name: hp server rx3600, BIOS 04.03 04/08/2008
> ...
> Call Trace:
> [<a000000100015210>] show_stack+0x90/0xc0
> [<a000000101163390>] dump_stack+0x150/0x1c0
> [<a0000001003f1e90>] __kernel_unpoison_pages+0x410/0x440
> [<a0000001003c2460>] get_page_from_freelist+0x1460/0x2ca0
> [<a0000001003c6be0>] __alloc_pages_nodemask+0x3c0/0x660
> [<a0000001003ed690>] alloc_pages_vma+0xb0/0x500
> [<a00000010037deb0>] __handle_mm_fault+0x1230/0x1fe0
> [<a00000010037ef70>] handle_mm_fault+0x310/0x4e0
> [<a00000010005dc70>] ia64_do_page_fault+0x1f0/0xb80
> [<a00000010000ca00>] ia64_leave_kernel+0x0/0x270
> page_owner tracks the page as freed
> page allocated via order 0, migratetype Movable,
> gfp_mask 0x100dca(GFP_HIGHUSER_MOVABLE|__GFP_ZERO), pid 37, ts 8173444098740
> __reset_page_owner+0x40/0x200
> free_pcp_prepare+0x4d0/0x600
> free_unref_page+0x20/0x1c0
> __put_page+0x110/0x1a0
> migrate_pages+0x16d0/0x1dc0
> compact_zone+0xfc0/0x1aa0
> proactive_compact_node+0xd0/0x1e0
> kcompactd+0x550/0x600
> kthread+0x2c0/0x2e0
> call_payload+0x50/0x80
>
> Here we can see that page was freed by page migration but something
> managed to write to it afterwards.
>
> CC: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> CC: linux-mm@xxxxxxxxx
> Signed-off-by: Sergei Trofimovich <slyfox@xxxxxxxxxx>
> ---
> mm/page_poison.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/mm/page_poison.c b/mm/page_poison.c
> index 65cdf844c8ad..ef2a1eab13d7 100644
> --- a/mm/page_poison.c
> +++ b/mm/page_poison.c
> @@ -4,6 +4,7 @@
> #include <linux/mm.h>
> #include <linux/highmem.h>
> #include <linux/page_ext.h>
> +#include <linux/page_owner.h>
> #include <linux/poison.h>
> #include <linux/ratelimit.h>
> #include <linux/kasan.h>
> @@ -45,7 +46,7 @@ static bool single_bit_flip(unsigned char a, unsigned char b)
> return error && !(error & (error - 1));
> }
>
> -static void check_poison_mem(unsigned char *mem, size_t bytes)
> +static void check_poison_mem(struct page *page, unsigned char *mem, size_t bytes)
> {
> static DEFINE_RATELIMIT_STATE(ratelimit, 5 * HZ, 10);
> unsigned char *start;
> @@ -70,6 +71,7 @@ static void check_poison_mem(unsigned char *mem, size_t bytes)
> print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start,
> end - start + 1, 1);
> dump_stack();
> + dump_page_owner(page);
OK but why not a full dump_page()?
> }
>
> static void unpoison_page(struct page *page)
> @@ -82,7 +84,7 @@ static void unpoison_page(struct page *page)
> * that is freed to buddy. Thus no extra check is done to
> * see if a page was poisoned.
> */
> - check_poison_mem(addr, PAGE_SIZE);
> + check_poison_mem(page, addr, PAGE_SIZE);
> kunmap_atomic(addr);
> }
>
>
