Try this, as root:
[root@mnm akpm]# /var/log/messages
bash: /var/log/messages: Text file busy
Strange return value, that.
It happens because vfs_permission() sees CAP_DAC_OVERRIDE
and returns "yes" on a file which has no `x' bits set.
Then open_exec() falls through to deny_write_access() which
sees that the file is open for writing.
If the file is _not_ open for writing then the "WTF" test in
prepare_binprm() is what stops us from executing the file. So
the test there is definitely needed.
Moving the "WTF" test into open_exec() definitely fixes things
up, but I think the real bug is in vfs_permission().
--- linux-2.4.6-pre6/fs/exec.c Wed May 2 22:00:06 2001
+++ lk-ext3/fs/exec.c Mon Jul 2 02:01:52 2001
@@ -349,6 +349,8 @@
file = ERR_PTR(-EACCES);
if (!IS_NOEXEC(inode) && S_ISREG(inode->i_mode)) {
int err = permission(inode, MAY_EXEC);
+ if (!err && !(inode->i_mode & 0111))
+ err = -EACCES;
file = ERR_PTR(err);
if (!err) {
file = dentry_open(nd.dentry, nd.mnt, O_RDONLY);
@@ -606,7 +608,10 @@
struct inode * inode = bprm->file->f_dentry->d_inode;
mode = inode->i_mode;
- /* Huh? We had already checked for MAY_EXEC, WTF do we check this? */
+ /*
+ * Check execute perms again - if the caller has CAP_DAC_OVERRIDE,
+ * vfs_permission lets a non-executable through
+ */
if (!(mode & 0111)) /* with at least _one_ execute bit set */
return -EACCES;
if (bprm->file->f_op == NULL)
-
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