path: root/mm/swapfile.c
diff options
authorCesar Eduardo Barros <cesarb@cesarb.net>2011-03-22 23:03:13 -0300
committerLinus Torvalds <torvalds@linux-foundation.org>2011-03-23 07:54:22 -0700
commit2130781e2aaab66e5a9f2fdc8af35da0153f405c (patch)
treeccd654b948587a39b219f74e6cfd73ef6daa3658 /mm/swapfile.c
parent04948c7f80b9446009c1c4791bb93e79729724fb (diff)
sys_swapon: fix inode locking
A conflict between 52c50567d8ab ("mm: swap: unlock swapfile inode mutex before closing file on bad swapfiles") and 83ef99befc32 ("sys_swapon: remove did_down variable") caused a double unlock of the inode mutex (once in bad_swap: before the filp_close, once at the end just before returning). The patch which added the extra unlock cleared did_down to avoid unlocking twice, but the other patch removed the did_down variable. To fix, set inode to NULL after the first unlock, since it will be used after that point only for the final unlock. While checking this patch, I found a path which could unlock without locking, in case the same inode was added as a swapfile twice. To fix, move the setting of the inode variable further down, to just before claim_swapfile, which will lock the inode before doing anything else. Cc: Mel Gorman <mgorman@suse.de> Cc: Hugh Dickins <hughd@google.com> Cc: Eric B Munson <emunson@mgebm.net> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/swapfile.c')
1 files changed, 5 insertions, 2 deletions
diff --git a/mm/swapfile.c b/mm/swapfile.c
index aafcf3611b3..71b42ec55b7 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -2088,7 +2088,6 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
p->swap_file = swap_file;
mapping = swap_file->f_mapping;
- inode = mapping->host;
for (i = 0; i < nr_swapfiles; i++) {
struct swap_info_struct *q = swap_info[i];
@@ -2101,6 +2100,8 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
+ inode = mapping->host;
+ /* If S_ISREG(inode->i_mode) will do mutex_lock(&inode->i_mutex); */
error = claim_swapfile(p, inode);
if (unlikely(error))
goto bad_swap;
@@ -2187,8 +2188,10 @@ bad_swap:
if (swap_file) {
- if (inode && S_ISREG(inode->i_mode))
+ if (inode && S_ISREG(inode->i_mode)) {
+ inode = NULL;
+ }
filp_close(swap_file, NULL);