Commit 43a4f261 authored Oct 03, 2017 by Oleg Nesterov Committed by Linus Torvalds Oct 03, 2017

exec: binfmt_misc: fix race between load_misc_binary() and kill_node()

load_misc_binary() makes a local copy of fmt->interpreter under
entries_lock to avoid the race with kill_node() but this is not enough;
the whole Node can be freed after we drop entries_lock, not only the
->interpreter string.

Add dget/dput(fmt->dentry) to ensure bm_evict_inode() can't destroy/free
this Node.

Link: http://lkml.kernel.org/r/20170922143650.GA17227@redhat.com


Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Ben Woodard <woodard@redhat.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Jim Foraker <foraker1@llnl.gov>
Cc: Travis Gummels <tgummels@redhat.com>
Cc: <tdhooge@llnl.gov>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent eb23aa03

fs/binfmt_misc.c

+8 −4

Original line number	Diff line number	Diff line
		@@ -138,20 +138,23 @@ static int load_misc_binary(struct linux_binprm *bprm)

		retval = -ENOEXEC;
		if (!enabled)
		goto ret;
		return retval;

		/* to keep locking time low, we copy the interpreter string */
		read_lock(&entries_lock);
		fmt = check_file(bprm);
		if (fmt)
		if (fmt) {
		dget(fmt->dentry);
		strlcpy(iname, fmt->interpreter, BINPRM_BUF_SIZE);
		}
		read_unlock(&entries_lock);
		if (!fmt)
		goto ret;
		return retval;

		/* Need to be able to load the file after exec */
		retval = -ENOENT;
		if (bprm->interp_flags & BINPRM_FLAGS_PATH_INACCESSIBLE)
		return -ENOENT;
		goto ret;

		if (!(fmt->flags & MISC_FMT_PRESERVE_ARGV0)) {
		retval = remove_arg_zero(bprm);
		@@ -238,6 +241,7 @@ static int load_misc_binary(struct linux_binprm *bprm)
		goto error;

		ret:
		dput(fmt->dentry);
		return retval;
		error:
		if (fd_binary > 0)