compat_do_execve should unshare_files

commit 53e9309e01277ec99c38e84e0ca16921287cf470 upstream.

2.6.26's commit fd8328be874f4190a811c58cd4778ec2c74d2c05
"sanitize handling of shared descriptor tables in failing execve()"
moved the unshare_files() from flush_old_exec() and several binfmts
to the head of do_execve(); but forgot to make the same change to
compat_do_execve(), leaving a CLONE_FILES files_struct shared across
exec from a 32-bit process on a 64-bit kernel.

It's arguable whether the files_struct really ought to be unshared
across exec; but 2.6.1 made that so to stop the loading binary's fd
leaking into other threads, and a 32-bit process on a 64-bit kernel
ought to behave in the same way as 32 on 32 and 64 on 64.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/fs/compat.c b/fs/compat.c
index d0145ca27572890b958765c72795a2b291628c20..2b1a8c44240482667527a85eac0aefafe30c984d 100644 (file)
--- a/fs/compat.c
+++ b/fs/compat.c
@@ -1392,12 +1392,17 @@ int compat_do_execve(char * filename,
 {
        struct linux_binprm *bprm;
        struct file *file;
+       struct files_struct *displaced;
        int retval;
 
+       retval = unshare_files(&displaced);
+       if (retval)
+               goto out_ret;
+
        retval = -ENOMEM;
        bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
        if (!bprm)
-               goto out_ret;
+               goto out_files;
 
        retval = mutex_lock_interruptible(&current->cred_exec_mutex);
        if (retval < 0)
@@ -1457,6 +1462,8 @@ int compat_do_execve(char * filename,
        mutex_unlock(&current->cred_exec_mutex);
        acct_update_integrals(current);
        free_bprm(bprm);
+       if (displaced)
+               put_files_struct(displaced);
        return retval;
 
 out:
@@ -1475,6 +1482,9 @@ out_unlock:
 out_free:
        free_bprm(bprm);
 
+out_files:
+       if (displaced)
+               reset_files_struct(displaced);
 out_ret:
        return retval;
 }