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authorAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>2011-01-29 16:13:42 +0300
committerAl Viro <viro@zeniv.linux.org.uk>2011-03-16 00:16:05 +0300
commit11a7b371b64ef39fc5fb1b6f2218eef7c4d035e3 (patch)
tree7d2059c9570e24c7d742eedfeedf19743d05a744 /fs/namei.c
parent326be7b484843988afe57566b627fb7a70beac56 (diff)
downloadlinux-11a7b371b64ef39fc5fb1b6f2218eef7c4d035e3.tar.xz
fs: allow AT_EMPTY_PATH in linkat(), limit that to CAP_DAC_READ_SEARCH
We don't want to allow creation of private hardlinks by different application using the fd passed to them via SCM_RIGHTS. So limit the null relative name usage in linkat syscall to CAP_DAC_READ_SEARCH Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Diffstat (limited to 'fs/namei.c')
-rw-r--r--fs/namei.c20
1 files changed, 16 insertions, 4 deletions
diff --git a/fs/namei.c b/fs/namei.c
index 9d4f32700179..c9b7f5b7e92a 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2945,15 +2945,27 @@ SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
struct dentry *new_dentry;
struct nameidata nd;
struct path old_path;
+ int how = 0;
int error;
char *to;
- if ((flags & ~AT_SYMLINK_FOLLOW) != 0)
+ if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0)
return -EINVAL;
+ /*
+ * To use null names we require CAP_DAC_READ_SEARCH
+ * This ensures that not everyone will be able to create
+ * handlink using the passed filedescriptor.
+ */
+ if (flags & AT_EMPTY_PATH) {
+ if (!capable(CAP_DAC_READ_SEARCH))
+ return -ENOENT;
+ how = LOOKUP_EMPTY;
+ }
+
+ if (flags & AT_SYMLINK_FOLLOW)
+ how |= LOOKUP_FOLLOW;
- error = user_path_at(olddfd, oldname,
- flags & AT_SYMLINK_FOLLOW ? LOOKUP_FOLLOW : 0,
- &old_path);
+ error = user_path_at(olddfd, oldname, how, &old_path);
if (error)
return error;