Re: [PATCH] Do _not_ call unlink on a directory

Matthieu Moy wrote:

Thomas Glanzmann [off-list ref] writes:

I believe you still have a race condition if ...

quoted

-				if (len > state->base_dir_len && state->force && !unlink(buf) && !mkdir(buf, 0777))
-					continue;

... buf exists here as a file ...

quoted

 				if (!stat(buf, &st) && S_ISDIR(st.st_mode))
 					continue; /* ok */

... and became a directory here.

quoted

+				if (len > state->base_dir_len && state->force && !unlink(buf) && !mkdir(buf, 0777))
+					continue;

But that's quite unlikely to happen. And I have no fix to propose.

If arbitrary other tasks are running, the only way to be absolutely
certain you're not calling unlink() in a directory is to never call
unlink().

SUS describes a safe remove(), but Solaris's implementation contains the
same race:

http://src.opensolaris.org/source/xref/pef/phase_I/usr/src/lib/libc/port/gen/rename.c

so I think this patch is the best that can be done.

Best regards,
Scott

-- 
Scott Lamb <http://www.slamb.org/>