From 2dab597441667d6c04451a7dcf215241ad4c74f6 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Fri, 11 Feb 2011 15:53:38 -0800 Subject: [PATCH] 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 Acked-by: Al Viro Cc: Nick Piggin Cc: Andrew Morton Signed-off-by: Linus Torvalds --- fs/namei.c | 20 ++++++++++---------- fs/open.c | 2 ++ 2 files changed, 12 insertions(+), 10 deletions(-) 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 @@ static inline int nameidata_drop_rcu_last_maybe(struct nameidata *nd) */ 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 @@ static struct file *finish_open(struct nameidata *nd, 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_mutex_unlock: 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 @@ struct file *do_filp_open(int dfd, const char *pathname, } 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 @@ out: 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 @@ exit_dput: 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; } diff --git a/fs/open.c b/fs/open.c index e52389e..5a2c6eb 100644 --- a/fs/open.c +++ b/fs/open.c @@ -790,6 +790,8 @@ struct file *nameidata_to_filp(struct nameidata *nd) /* Pick up the filp from the open intent */ filp = nd->intent.open.file; + nd->intent.open.file = NULL; + /* Has the filesystem initialised the file for us? */ if (filp->f_path.dentry == NULL) { path_get(&nd->path); -- 2.7.4