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authorLinus Torvalds <torvalds@linux-foundation.org>2011-02-11 15:53:38 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2011-02-11 15:53:38 -0800
commit2dab597441667d6c04451a7dcf215241ad4c74f6 (patch)
treef56a6f7fcabf3a9b82a5e77ef9c96268224efbd1
parentd2478521afc20227658a10a8c5c2bf1a2aa615b3 (diff)
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>
-rw-r--r--fs/namei.c20
-rw-r--r--fs/open.c2
2 files changed, 12 insertions, 10 deletions
diff --git a/fs/namei.c b/fs/namei.c
index 7d77f24d32a..ec4b2d0190a 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 e52389e1f05..5a2c6ebc22b 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);