path: root/mm
diff options
authorKrzysztof Kozlowski <k.kozlowski@samsung.com>2013-10-16 13:47:06 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-10-16 21:35:53 -0700
commit5b808a2300a5ac45f4798ebfac8b367e98a4b692 (patch)
treeb08db2864c1380eeb1c41f29ebeea1a2c29dd473 /mm
parentfad1a86e25e0a1f85635ed06ef62ddadd5b8fa4c (diff)
swap: fix set_blocksize race during swapon/swapoff
Fix race between swapoff and swapon. Swapoff used old_block_size from swap_info outside of swapon_mutex so it could be overwritten by concurrent swapon. The race has visible effect only if more than one swap block device exists with different block sizes (e.g. /dev/sda1 with block size 4096 and /dev/sdb1 with 512). In such case it leads to setting the blocksize of swapped off device with wrong blocksize. The bug can be triggered with multiple concurrent swapoff and swapon: 0. Swap for some device is on. 1. swapoff: First the swapoff is called on this device and "struct swap_info_struct *p" is assigned. This is done under swap_lock however this lock is released for the call try_to_unuse(). 2. swapon: After the assignment above (and before acquiring swapon_mutex & swap_lock by swapoff) the swapon is called on the same device. The p->old_block_size is assigned to the value of block_size the device. This block size should be the same as previous but sometimes it is not. The swapon ends successfully. 3. swapoff: Swapoff resumes, grabs the locks and mutex and continues to disable this swap device. Now it sets the block size to value taken from swap_info which was overwritten by swapon in 2. Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com> Reported-by: Weijie Yang <weijie.yang.kh@gmail.com> Cc: Bob Liu <bob.liu@oracle.com> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: Shaohua Li <shli@fusionio.com> Cc: Minchan Kim <minchan@kernel.org> Acked-by: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
1 files changed, 3 insertions, 1 deletions
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 3963fc24fcc..de7c904e52e 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1824,6 +1824,7 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
struct filename *pathname;
int i, type, prev;
int err;
+ unsigned int old_block_size;
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
@@ -1914,6 +1915,7 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
swap_file = p->swap_file;
+ old_block_size = p->old_block_size;
p->swap_file = NULL;
p->max = 0;
swap_map = p->swap_map;
@@ -1938,7 +1940,7 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
inode = mapping->host;
if (S_ISBLK(inode->i_mode)) {
struct block_device *bdev = I_BDEV(inode);
- set_blocksize(bdev, p->old_block_size);
+ set_blocksize(bdev, old_block_size);
blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
} else {