The patch titled
sys_swapon: fix inode locking
has been added to the -mm tree. Its filename is
sys_swapon-fix-inode-locking.patch
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------------------------------------------------------
Subject: sys_swapon: fix inode locking
From: Cesar Eduardo Barros <cesarb@xxxxxxxxxx>
A conflict between 52c50567d8ab0a0a87f12cceaa4194967854f0bd (mm: swap:
unlock swapfile inode mutex before closing file on bad swapfiles) and
83ef99befc324803a54cf2a5fab5a322df3a99d6 (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.
Signed-off-by: Cesar Eduardo Barros <cesarb@xxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Eric B Munson <emunson@xxxxxxxxx>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/swapfile.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff -puN mm/swapfile.c~sys_swapon-fix-inode-locking mm/swapfile.c
--- a/mm/swapfile.c~sys_swapon-fix-inode-locking
+++ a/mm/swapfile.c
@@ -2088,7 +2088,6 @@ SYSCALL_DEFINE2(swapon, const char __use
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 __use
}
}
+ 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:
spin_unlock(&swap_lock);
vfree(swap_map);
if (swap_file) {
- if (inode && S_ISREG(inode->i_mode))
+ if (inode && S_ISREG(inode->i_mode)) {
mutex_unlock(&inode->i_mutex);
+ inode = NULL;
+ }
filp_close(swap_file, NULL);
}
out:
_
Patches currently in -mm which might be from cesarb@xxxxxxxxxx are
sys_swapon-use-vzalloc-instead-of-vmalloc-memset.patch
sys_swapon-remove-changelog-from-function-comment.patch
sys_swapon-do-not-depend-on-type-after-allocation.patch
sys_swapon-separate-swap_info-allocation.patch
sys_swapon-simplify-error-return-from-swap_info-allocation.patch
sys_swapon-simplify-error-flow-in-alloc_swap_info.patch
sys_swapon-remove-initial-value-of-name-variable.patch
sys_swapon-remove-did_down-variable.patch
sys_swapon-move-setting-of-error-nearer-use.patch
sys_swapon-remove-bdev-variable.patch
sys_swapon-do-only-cleanup-in-the-cleanup-blocks.patch
sys_swapon-use-a-single-error-label.patch
sys_swapon-separate-bdev-claim-and-inode-lock.patch
sys_swapon-simplify-error-flow-in-claim_swapfile.patch
sys_swapon-move-setting-of-swapfilepages-near-use.patch
sys_swapon-separate-parsing-of-swapfile-header.patch
sys_swapon-simplify-error-flow-in-read_swap_header.patch
sys_swapon-call-swap_cgroup_swapon-earlier.patch
sys_swapon-separate-parsing-of-bad-blocks-and-extents.patch
sys_swapon-simplify-error-flow-in-setup_swap_map_and_extents.patch
sys_swapon-remove-nr_good_pages-variable.patch
sys_swapon-move-printk-outside-lock.patch
sys_swapoff-change-order-to-match-sys_swapon.patch
sys_swapon-separate-final-enabling-of-the-swapfile.patch
mm-remove-inline-from-scan_swap_map.patch
sys_swapon-fix-inode-locking.patch
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