fs/coredump: prevent fsuid=0 dumps into user-controlled directories

[pandora-kernel.git] / fs / exec.c

diff --git a/fs/exec.c b/fs/exec.c
index aba5e13..a0006d8 100644 (file)
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -55,6 +55,9 @@
 #include <linux/pipe_fs_i.h>
 #include <linux/oom.h>
 #include <linux/compat.h>
+#include <linux/sched.h>
+#include <linux/fs.h>
+#include <linux/path.h>
 
 #include <asm/uaccess.h>
 #include <asm/mmu_context.h>
@@ -2246,6 +2249,8 @@ void do_coredump(long signr, int exit_code, struct pt_regs *regs)
                }
        } else {
                struct inode *inode;
+               int open_flags = O_CREAT | O_RDWR | O_NOFOLLOW |
+                                O_LARGEFILE | O_EXCL;
 
                if (cprm.limit < binfmt->min_coredump)
                        goto fail_unlock;
@@ -2284,10 +2289,27 @@ void do_coredump(long signr, int exit_code, struct pt_regs *regs)
                 * what matters is that at least one of the two processes
                 * writes its coredump successfully, not which one.
                 */
-               cprm.file = filp_open(cn.corename,
-                                O_CREAT | 2 | O_NOFOLLOW |
-                                O_LARGEFILE | O_EXCL,
-                                0600);
+               if (need_suid_safe) {
+                       /*
+                        * Using user namespaces, normal user tasks can change
+                        * their current->fs->root to point to arbitrary
+                        * directories. Since the intention of the "only dump
+                        * with a fully qualified path" rule is to control where
+                        * coredumps may be placed using root privileges,
+                        * current->fs->root must not be used. Instead, use the
+                        * root directory of init_task.
+                        */
+                       struct path root;
+
+                       task_lock(&init_task);
+                       get_fs_root(init_task.fs, &root);
+                       task_unlock(&init_task);
+                       cprm.file = file_open_root(root.dentry, root.mnt,
+                               cn.corename, open_flags, 0600);
+                       path_put(&root);
+               } else {
+                       cprm.file = filp_open(cn.corename, open_flags, 0600);
+               }
                if (IS_ERR(cprm.file))
                        goto fail_unlock;