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authorKirill A. Shutemov <kirill.shutemov@linux.intel.com>2016-01-21 16:40:27 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2016-01-21 17:20:51 -0800
commit7162a1e87b3e380133dadc7909081bb70d0a7041 (patch)
treeffb80447191bb2d64a8ee28a0823c46379b01d94 /mm/mlock.c
parentb6ec57f4b92e9bae4617f7d98a054d45370284bb (diff)
downloadlinux-7162a1e87b3e380133dadc7909081bb70d0a7041.tar.bz2
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/mlock.c')
-rw-r--r--mm/mlock.c2
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 */