Messages in this thread Patch in this message |  | | | From | "Rafael J. Wysocki" <> | | Subject | [PATCH] PM / Hibernate: Fix free_unnecessary_pages() | | Date | Wed, 6 Jul 2011 20:46:23 +0200 |
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From: Rafael J. Wysocki <rjw@sisk.pl>
There is a bug in free_unnecessary_pages() that causes it to attempt to free too many pages in some cases, which triggers the BUG_ON() in memory_bm_clear_bit() for copy_bm. Namely, if count_data_pages() is initially greater than alloc_normal, we get to_free_normal equal to 0 and "save" greater from 0. In that case, if the sum of "save" and count_highmem_pages() is greater than alloc_highmem, we subtract a positive number from to_free_normal. Hence, since to_free_normal was 0 before the subtraction and is an unsigned int, the result is converted to a huge positive number that is used as the number of pages to free.
Fix this bug by checking if to_free_normal is actually greater than or equal to the number we're going to subtract from it.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl> Reported-and-tested-by: Matthew Garrett <mjg@redhat.com> Cc: stable@kernel.org --- kernel/power/snapshot.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) Index: linux-2.6/kernel/power/snapshot.c =================================================================== --- linux-2.6.orig/kernel/power/snapshot.c +++ linux-2.6/kernel/power/snapshot.c @@ -1211,7 +1211,11 @@ static void free_unnecessary_pages(void) to_free_highmem = alloc_highmem - save; } else { to_free_highmem = 0; - to_free_normal -= save - alloc_highmem; + save -= alloc_highmem; + if (to_free_normal > save) + to_free_normal -= save; + else + to_free_normal = 0; } memory_bm_position_reset(©_bm);
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