Commit 2dab5974 authored by Linus Torvalds's avatar Linus Torvalds

Fix possible filp_cachep memory corruption

In commit 31e6b01f ("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: default avatarJ. R. Okajima <hooanon05@yahoo.co.jp>
Acked-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
Cc: Nick Piggin <npiggin@kernel.dk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent d2478521
......@@ -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;
}
......
......@@ -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);
......
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