Commit 92eaa565 authored Sep 11, 2013 by Oleg Nesterov Committed by Linus Torvalds Sep 11, 2013

exec: kill ->load_binary != NULL check in search_binary_handler()



search_binary_handler() checks ->load_binary != NULL for no reason, this
method should be always defined.  Turn this check into WARN_ON() and move
it into __register_binfmt().

Also, kill the function pointer.  The current code looks confusing, as if
->load_binary can go away after read_unlock(&binfmt_lock).  But we rely on
module_get(fmt->module), this fmt can't be changed or unregistered,
otherwise this code is buggy anyway.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Evgeniy Polyakov <zbr@ioremap.net>
Cc: Zach Levis <zml@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 52f14282

fs/exec.c

+3 −4

Original line number	Diff line number	Diff line
		@@ -74,6 +74,8 @@ static DEFINE_RWLOCK(binfmt_lock);
		void __register_binfmt(struct linux_binfmt * fmt, int insert)
		{
		BUG_ON(!fmt);
		if (WARN_ON(!fmt->load_binary))
		return;
		write_lock(&binfmt_lock);
		insert ? list_add(&fmt->lh, &formats) :
		list_add_tail(&fmt->lh, &formats);
		@@ -1389,14 +1391,11 @@ int search_binary_handler(struct linux_binprm *bprm)
		for (try=0; try<2; try++) {
		read_lock(&binfmt_lock);
		list_for_each_entry(fmt, &formats, lh) {
		int (fn)(struct linux_binprm ) = fmt->load_binary;
		if (!fn)
		continue;
		if (!try_module_get(fmt->module))
		continue;
		read_unlock(&binfmt_lock);
		bprm->recursion_depth++;
		retval = fn(bprm);
		retval = fmt->load_binary(bprm);
		bprm->recursion_depth--;
		if (retval >= 0) {
		put_binfmt(fmt);