On 2023/9/27 22:39, Dan Carpenter wrote:
On Wed, Sep 27, 2023 at 05:02:26PM +0300, Amir Goldstein wrote:
On Mon, Sep 25, 2023 at 7:52 AM Su Hui <suhui@xxxxxxxxxxxx> wrote:
smatch warn:
fs/overlayfs/copy_up.c:450 ovl_set_origin() warn:
variable dereferenced before check 'fh' (see line 449)
If 'fh' is NULL, passing NULL instead of 'fh->buf'.
Signed-off-by: Su Hui <suhui@xxxxxxxxxxxx>
---
fs/overlayfs/copy_up.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index d1761ec5866a..086f9176b4d4 100644
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -446,7 +446,7 @@ int ovl_set_origin(struct ovl_fs *ofs, struct dentry *lower,
/*
* Do not fail when upper doesn't support xattrs.
*/
- err = ovl_check_setxattr(ofs, upper, OVL_XATTR_ORIGIN, fh->buf,
+ err = ovl_check_setxattr(ofs, upper, OVL_XATTR_ORIGIN, fh ? fh->buf : NULL,
fh ? fh->fb.len : 0, 0);
kfree(fh);
--
2.30.2
After discussing this with Dan Carpenter, this is not a kernel bug,
it is a smatch bug.
Yeah. Sorry about that, Su Hui. The ->buf struct member is not a
pointer, it's an array. So this isn't really a dereference, it's just
pointer math and foo = fh->buf won't crash even if fh is NULL.
Got it, I'm so careless that make this wrong patch.
Really thanks for your reminder!
Su Hui
I have written a fix for this in Smatch. I'll test it a bit before I
push it.
regards,
dan carpenter
