Fix possible filp_cachep memory corruption
In commit 31e6b01f4183 ("fs: rcu-walk for path lookup") we started doing
path lookup using RCU, which then falls back to a careful non-RCU lookup
in case of problems (LOOKUP_REVAL). So do_filp_open() has this "re-do
the lookup carefully" looping case.
However, that means that we must not release the open-intent file data
if we are going to loop around and use it once more!
Fix this by moving the release of the open-intent data to the function
that allocates it (do_filp_open() itself) rather than the helper
functions that can get called multiple times (finish_open() and
do_last()). This makes the logic for the lifetime of that field much
more obvious, and avoids the possible double free.
Reported-by: J. R. Okajima <hooanon05@yahoo.co.jp>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Cc: Nick Piggin <npiggin@kernel.dk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/namei.c b/fs/namei.c
index 7d77f24..ec4b2d0 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -561,10 +561,14 @@
*/
void release_open_intent(struct nameidata *nd)
{
- if (nd->intent.open.file->f_path.dentry == NULL)
- put_filp(nd->intent.open.file);
- else
- fput(nd->intent.open.file);
+ struct file *file = nd->intent.open.file;
+
+ if (file && !IS_ERR(file)) {
+ if (file->f_path.dentry == NULL)
+ put_filp(file);
+ else
+ fput(file);
+ }
}
/*
@@ -2265,8 +2269,6 @@
return filp;
exit:
- if (!IS_ERR(nd->intent.open.file))
- release_open_intent(nd);
path_put(&nd->path);
return ERR_PTR(error);
}
@@ -2389,8 +2391,6 @@
exit_dput:
path_put_conditional(path, nd);
exit:
- if (!IS_ERR(nd->intent.open.file))
- release_open_intent(nd);
path_put(&nd->path);
return ERR_PTR(error);
}
@@ -2477,6 +2477,7 @@
}
audit_inode(pathname, nd.path.dentry);
filp = finish_open(&nd, open_flag, acc_mode);
+ release_open_intent(&nd);
return filp;
creat:
@@ -2553,6 +2554,7 @@
path_put(&nd.root);
if (filp == ERR_PTR(-ESTALE) && !(flags & LOOKUP_REVAL))
goto reval;
+ release_open_intent(&nd);
return filp;
exit_dput:
@@ -2560,8 +2562,6 @@
out_path:
path_put(&nd.path);
out_filp:
- if (!IS_ERR(nd.intent.open.file))
- release_open_intent(&nd);
filp = ERR_PTR(error);
goto out;
}