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Subject[PATCH 03/30] check for null vfsmount in dentry_open()
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Make sure no-one calls dentry_open with a NULL vfsmount argument and crap
out with a stacktrace otherwise. A NULL file->f_vfsmnt has always been
problematic, but with the per-mount r/o tracking we can't accept anymore
at all.

Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
---

linux-2.6.git-dave/fs/open.c | 12 ++++++++++++
1 file changed, 12 insertions(+)

diff -puN fs/open.c~check-for-NULL-vfsmount-in-dentry-open fs/open.c
--- linux-2.6.git/fs/open.c~check-for-NULL-vfsmount-in-dentry-open 2008-02-15 13:25:42.000000000 -0800
+++ linux-2.6.git-dave/fs/open.c 2008-02-15 13:25:42.000000000 -0800
@@ -903,6 +903,18 @@ struct file *dentry_open(struct dentry *
int error;
struct file *f;

+ /*
+ * We must always pass in a valid mount pointer. Historically
+ * callers got away with not passing it, but we must enforce this at
+ * the earliest possible point now to avoid strange problems deep in the
+ * filesystem stack.
+ */
+ if (!mnt) {
+ printk(KERN_WARNING "%s called with NULL vfsmount\n", __func__);
+ dump_stack();
+ return ERR_PTR(-EINVAL);
+ }
+
error = -ENFILE;
f = get_empty_filp();
if (f == NULL) {
_

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