On Sun, 7 May 2006, Linus Torvalds wrote:
>
> Trond wrote an alternate patch for the actual problem which I sent
> separately, but it would probably be good to have more safety in the slab
> layer by default regardless.
And here's Trond's suggested locks.c fix.
Linus
---
From: Trond Myklebust <[email protected]>
Subject: fs/locks.c: Fix lease_init
Date: Sun, 07 May 2006 23:02:42 -0400
It is insane to be giving lease_init() the task of freeing the lock it is
supposed to initialise, given that the lock is not guaranteed to be
allocated on the stack. This causes lockups in fcntl_setlease().
Problem diagnosed by Daniel Hokka Zakrisson <[email protected]>
Also fix a slab leak in __setlease() due to an uninitialised return value.
Problem diagnosed by Björn Steinbrink.
Signed-off-by: Trond Myklebust <[email protected]>
---
fs/locks.c | 21 ++++++++++++---------
1 files changed, 12 insertions(+), 9 deletions(-)
diff --git a/fs/locks.c b/fs/locks.c
index abd9448..64b96b1 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -446,15 +446,14 @@ static struct lock_manager_operations le
*/
static int lease_init(struct file *filp, int type, struct file_lock *fl)
{
+ if (assign_type(fl, type) != 0)
+ return -EINVAL;
+
fl->fl_owner = current->files;
fl->fl_pid = current->tgid;
fl->fl_file = filp;
fl->fl_flags = FL_LEASE;
- if (assign_type(fl, type) != 0) {
- locks_free_lock(fl);
- return -EINVAL;
- }
fl->fl_start = 0;
fl->fl_end = OFFSET_MAX;
fl->fl_ops = NULL;
@@ -466,16 +465,19 @@ static int lease_init(struct file *filp,
static int lease_alloc(struct file *filp, int type, struct file_lock **flp)
{
struct file_lock *fl = locks_alloc_lock();
- int error;
+ int error = -ENOMEM;
if (fl == NULL)
- return -ENOMEM;
+ goto out;
error = lease_init(filp, type, fl);
- if (error)
- return error;
+ if (error) {
+ locks_free_lock(fl);
+ fl = NULL;
+ }
+out:
*flp = fl;
- return 0;
+ return error;
}
/* Check if two locks overlap each other.
@@ -1391,6 +1393,7 @@ static int __setlease(struct file *filp,
goto out;
if (my_before != NULL) {
+ *flp = *my_before;
error = lease->fl_lmops->fl_change(my_before, arg);
goto out;
}
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