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authorStephen Brennan <stephen.s.brennan@oracle.com>2021-09-01 10:51:41 -0700
committerAl Viro <viro@zeniv.linux.org.uk>2021-09-07 15:56:16 -0400
commit0766ec82e5fb26fc5dc6d592bc61865608bdc651 (patch)
treeddc2d8422eab2d84d23f6ac91e8a3a89b15cee36 /fs/namei.c
parent4b93c544e90e2b28326182d31ee008eb80e02074 (diff)
namei: Fix use after free in kern_path_locked
In 0ee50b47532a ("namei: change filename_parentat() calling conventions"), filename_parentat() was made to always call putname() on the filename before returning, and kern_path_locked() was migrated to this calling convention. However, kern_path_locked() uses the "last" parameter to lookup and potentially create a new dentry. The last parameter contains the last component of the path and points within the filename, which was recently freed at the end of filename_parentat(). Thus, when kern_path_locked() calls __lookup_hash(), it is using the filename after it has already been freed. In other words, these calling conventions had been wrong for the only remaining caller of filename_parentat(). Everything else is using __filename_parentat(), which does not drop the reference; so should kern_path_locked(). Switch kern_path_locked() to use of __filename_parentat() and move getting/dropping struct filename into wrapper. Remove filename_parentat(), now that we have no remaining callers. Fixes: 0ee50b47532a ("namei: change filename_parentat() calling conventions") Link: https://lore.kernel.org/linux-fsdevel/YS9D4AlEsaCxLFV0@infradead.org/ Link: https://lore.kernel.org/linux-fsdevel/YS+csMTV2tTXKg3s@zeniv-ca.linux.org.uk/ Cc: Christoph Hellwig <hch@infradead.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Reported-by: syzbot+fb0d60a179096e8c2731@syzkaller.appspotmail.com Signed-off-by: Stephen Brennan <stephen.s.brennan@oracle.com> Co-authored-by: Dmitry Kadashev <dkadashev@gmail.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/namei.c')
-rw-r--r--fs/namei.c29
1 files changed, 14 insertions, 15 deletions
diff --git a/fs/namei.c b/fs/namei.c
index 95a881e0552b..33a2a8504099 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2514,9 +2514,10 @@ static int path_parentat(struct nameidata *nd, unsigned flags,
return err;
}
+/* Note: this does not consume "name" */
static int __filename_parentat(int dfd, struct filename *name,
- unsigned int flags, struct path *parent,
- struct qstr *last, int *type)
+ unsigned int flags, struct path *parent,
+ struct qstr *last, int *type)
{
int retval;
struct nameidata nd;
@@ -2538,25 +2539,14 @@ static int __filename_parentat(int dfd, struct filename *name,
return retval;
}
-static int filename_parentat(int dfd, struct filename *name,
- unsigned int flags, struct path *parent,
- struct qstr *last, int *type)
-{
- int retval = __filename_parentat(dfd, name, flags, parent, last, type);
-
- putname(name);
- return retval;
-}
-
/* does lookup, returns the object with parent locked */
-struct dentry *kern_path_locked(const char *name, struct path *path)
+static struct dentry *__kern_path_locked(struct filename *name, struct path *path)
{
struct dentry *d;
struct qstr last;
int type, error;
- error = filename_parentat(AT_FDCWD, getname_kernel(name), 0, path,
- &last, &type);
+ error = __filename_parentat(AT_FDCWD, name, 0, path, &last, &type);
if (error)
return ERR_PTR(error);
if (unlikely(type != LAST_NORM)) {
@@ -2572,6 +2562,15 @@ struct dentry *kern_path_locked(const char *name, struct path *path)
return d;
}
+struct dentry *kern_path_locked(const char *name, struct path *path)
+{
+ struct filename *filename = getname_kernel(name);
+ struct dentry *res = __kern_path_locked(filename, path);
+
+ putname(filename);
+ return res;
+}
+
int kern_path(const char *name, unsigned int flags, struct path *path)
{
return filename_lookup(AT_FDCWD, getname_kernel(name),