[PATCH 1/4] compat_do_execve should unshare_files

Hugh Dickins
2009-03-28T23:17:27Z

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
---

fs/compat.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)

--- 2.6.29/fs/compat.c 2009-03-23 23:12:14.000000000 +0000
+++ linux/fs/compat.c 2009-03-28 18:06:02.000000000 +0000
@@ -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;
}