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authorAndy Adamson <andros@citi.umich.edu>2006-03-20 13:44:26 -0500
committerTrond Myklebust <Trond.Myklebust@netapp.com>2006-03-20 13:44:26 -0500
commit8dc7c3115b611c00006eac3ee5b108296432aab7 (patch)
treebe44c59907cbdcb6fdf46d0ad9cc140af757acfc /fs/locks.c
parent2e0af86f618c697b44e2d67dff151256c58201c4 (diff)
downloadlinux-8dc7c3115b611c00006eac3ee5b108296432aab7.tar.bz2
locks,lockd: fix race in nlmsvc_testlock
posix_test_lock() returns a pointer to a struct file_lock which is unprotected and can be removed while in use by the caller. Move the conflicting lock from the return to a parameter, and copy the conflicting lock. In most cases the caller ends up putting the copy of the conflicting lock on the stack. On i386, sizeof(struct file_lock) appears to be about 100 bytes. We're assuming that's reasonable. Signed-off-by: Andy Adamson <andros@citi.umich.edu> Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu> Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Diffstat (limited to 'fs/locks.c')
-rw-r--r--fs/locks.c21
1 files changed, 13 insertions, 8 deletions
diff --git a/fs/locks.c b/fs/locks.c
index cb940b142c5f..231b23c12c3d 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -672,8 +672,9 @@ static int locks_block_on_timeout(struct file_lock *blocker, struct file_lock *w
return result;
}
-struct file_lock *
-posix_test_lock(struct file *filp, struct file_lock *fl)
+int
+posix_test_lock(struct file *filp, struct file_lock *fl,
+ struct file_lock *conflock)
{
struct file_lock *cfl;
@@ -684,9 +685,13 @@ posix_test_lock(struct file *filp, struct file_lock *fl)
if (posix_locks_conflict(cfl, fl))
break;
}
+ if (cfl) {
+ locks_copy_lock(conflock, cfl);
+ unlock_kernel();
+ return 1;
+ }
unlock_kernel();
-
- return (cfl);
+ return 0;
}
EXPORT_SYMBOL(posix_test_lock);
@@ -1563,7 +1568,7 @@ asmlinkage long sys_flock(unsigned int fd, unsigned int cmd)
*/
int fcntl_getlk(struct file *filp, struct flock __user *l)
{
- struct file_lock *fl, file_lock;
+ struct file_lock *fl, cfl, file_lock;
struct flock flock;
int error;
@@ -1587,7 +1592,7 @@ int fcntl_getlk(struct file *filp, struct flock __user *l)
else
fl = (file_lock.fl_type == F_UNLCK ? NULL : &file_lock);
} else {
- fl = posix_test_lock(filp, &file_lock);
+ fl = (posix_test_lock(filp, &file_lock, &cfl) ? &cfl : NULL);
}
flock.l_type = F_UNLCK;
@@ -1717,7 +1722,7 @@ out:
*/
int fcntl_getlk64(struct file *filp, struct flock64 __user *l)
{
- struct file_lock *fl, file_lock;
+ struct file_lock *fl, cfl, file_lock;
struct flock64 flock;
int error;
@@ -1741,7 +1746,7 @@ int fcntl_getlk64(struct file *filp, struct flock64 __user *l)
else
fl = (file_lock.fl_type == F_UNLCK ? NULL : &file_lock);
} else {
- fl = posix_test_lock(filp, &file_lock);
+ fl = (posix_test_lock(filp, &file_lock, &cfl) ? &cfl : NULL);
}
flock.l_type = F_UNLCK;