From: david m. richter <richterd@xxxxxxxxxxxxxx>
It is possible that another process could acquire a new file lease right
after break_lease() is called during a truncate, but before lease-granting
is disabled by the subsequent get_write_access(). Merely switching the
order of the break_lease() and get_write_access() calls prevents this race.
Signed-off-by: David M. Richter <richterd@xxxxxxxxxxxxxx>
Signed-off-by: "J. Bruce Fields" <bfields@xxxxxxxxxxxxxx>
---
fs/open.c | 16 +++++++++-------
1 files changed, 9 insertions(+), 7 deletions(-)
I posted this patch to linux-fsdevel last week and nobody said anything.
Thus, it is perfect.
--b.
diff --git a/fs/open.c b/fs/open.c
index 0d515d1..c32aba0 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -255,24 +255,26 @@ static long do_sys_truncate(const char __user * path, loff_t length)
if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
goto dput_and_out;
- /*
- * Make sure that there are no leases.
- */
- error = break_lease(inode, FMODE_WRITE);
+ error = get_write_access(inode);
if (error)
goto dput_and_out;
- error = get_write_access(inode);
+ /*
+ * Make sure that there are no leases. get_write_access() protects
+ * against the truncate racing with a lease-granting setlease().
+ */
+ error = break_lease(inode, FMODE_WRITE);
if (error)
- goto dput_and_out;
+ goto put_write_and_out;
error = locks_verify_truncate(inode, NULL, length);
if (!error) {
DQUOT_INIT(inode);
error = do_truncate(nd.dentry, length, 0, NULL);
}
- put_write_access(inode);
+put_write_and_out:
+ put_write_access(inode);
dput_and_out:
path_release(&nd);
out:
--
1.5.3.rc0.63.gc956
-
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