[PATCH] sanitize handling of shared descriptor tables in failing execve()

* unshare_files() can fail; doing it after irreversible actions is wrong
  and de_thread() is certainly irreversible.
* since we do it unconditionally anyway, we might as well do it in do_execve()
  and save ourselves the PITA in binfmt handlers, etc.
* while we are at it, binfmt_som actually leaked files_struct on failure.

As a side benefit, unshare_files(), put_files_struct() and reset_files_struct()
become unexported.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 1 insertions, 17 deletions

diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c
index b53c7e5f41bb..dbf0ac0523de 100644
--- a/fs/binfmt_misc.c
+++ b/fs/binfmt_misc.c
@@ -110,7 +110,6 @@ static int load_misc_binary(struct linux_binprm *bprm, struct pt_regs *regs)
         char *iname_addr = iname;
         int retval;
         int fd_binary = -1;
-        struct files_struct *files = NULL;
 
         retval = -ENOEXEC;
         if (!enabled)
@@ -133,21 +132,13 @@ static int load_misc_binary(struct linux_binprm *bprm, struct pt_regs *regs)
 
         if (fmt->flags & MISC_FMT_OPEN_BINARY) {
 
-                files = current->files;
-                retval = unshare_files();
-                if (retval < 0)
-                        goto _ret;
-                if (files == current->files) {
-                        put_files_struct(files);
-                        files = NULL;
-                }
                 /* if the binary should be opened on behalf of the
                  * interpreter than keep it open and assign descriptor
                  * to it */
                 fd_binary = get_unused_fd();
                 if (fd_binary < 0) {
                         retval = fd_binary;
-                        goto _unshare;
+                        goto _ret;
                 }
                 fd_install(fd_binary, bprm->file);
 
@@ -205,10 +196,6 @@ static int load_misc_binary(struct linux_binprm *bprm, struct pt_regs *regs)
         if (retval < 0)
                 goto _error;
 
-        if (files) {
-                put_files_struct(files);
-                files = NULL;
-        }
 _ret:
         return retval;
 _error:
@@ -216,9 +203,6 @@ _error:
                 sys_close(fd_binary);
         bprm->interp_flags = 0;
         bprm->interp_data = 0;
-_unshare:
-        if (files)
-                reset_files_struct(current, files);
         goto _ret;
 }