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author | 2016-01-21 16:40:27 -0800 | |
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committer | 2016-01-21 17:20:51 -0800 | |
commit | 7162a1e87b3e380133dadc7909081bb70d0a7041 (patch) | |
tree | ffb80447191bb2d64a8ee28a0823c46379b01d94 /mm | |
parent | thp: change pmd_trans_huge_lock() interface to return ptl (diff) | |
download | linux-7162a1e87b3e380133dadc7909081bb70d0a7041.tar.gz linux-7162a1e87b3e380133dadc7909081bb70d0a7041.tar.bz2 linux-7162a1e87b3e380133dadc7909081bb70d0a7041.zip |
mm: fix mlock accouting
Tetsuo Handa reported underflow of NR_MLOCK on munlock.
Testcase:
#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#define BASE ((void *)0x400000000000)
#define SIZE (1UL << 21)
int main(int argc, char *argv[])
{
void *addr;
system("grep Mlocked /proc/meminfo");
addr = mmap(BASE, SIZE, PROT_READ | PROT_WRITE,
MAP_ANONYMOUS | MAP_PRIVATE | MAP_LOCKED | MAP_FIXED,
-1, 0);
if (addr == MAP_FAILED)
printf("mmap() failed\n"), exit(1);
munmap(addr, SIZE);
system("grep Mlocked /proc/meminfo");
return 0;
}
It happens on munlock_vma_page() due to unfortunate choice of nr_pages
data type:
__mod_zone_page_state(zone, NR_MLOCK, -nr_pages);
For unsigned int nr_pages, implicitly casted to long in
__mod_zone_page_state(), it becomes something around UINT_MAX.
munlock_vma_page() usually called for THP as small pages go though
pagevec.
Let's make nr_pages signed int.
Similar fixes in 6cdb18ad98a4 ("mm/vmstat: fix overflow in
mod_zone_page_state()") used `long' type, but `int' here is OK for a
count of the number of sub-pages in a huge page.
Fixes: ff6a6da60b89 ("mm: accelerate munlock() treatment of THP pages")
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Tested-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Michel Lespinasse <walken@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: <stable@vger.kernel.org> [4.4+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r-- | mm/mlock.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/mlock.c b/mm/mlock.c index e1e2b1207bf2..96f001041928 100644 --- a/mm/mlock.c +++ b/mm/mlock.c @@ -175,7 +175,7 @@ static void __munlock_isolation_failed(struct page *page) */ unsigned int munlock_vma_page(struct page *page) { - unsigned int nr_pages; + int nr_pages; struct zone *zone = page_zone(page); /* For try_to_munlock() and to serialize with page migration */ |