Commit a75e78f2 authored Jul 07, 2018 by Bernd Edlinger Committed by Greg Kroah-Hartman Sep 16, 2018

kernfs: Fix range checks in kernfs_get_target_path



The terminating NUL byte is only there because the buffer is
allocated with kzalloc(PAGE_SIZE, GFP_KERNEL), but since the
range-check is off-by-one, and PAGE_SIZE==PATH_MAX, the
returned string may not be zero-terminated if it is exactly
PATH_MAX characters long.  Furthermore also the initial loop
may theoretically exceed PATH_MAX and cause a fault.

Signed-off-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent bdae566d

fs/kernfs/symlink.c

+4 −1

Original line number	Diff line number	Diff line
		@@ -72,6 +72,9 @@ static int kernfs_get_target_path(struct kernfs_node *parent,
		if (base == kn)
		break;

		if ((s - path) + 3 >= PATH_MAX)
		return -ENAMETOOLONG;

		strcpy(s, "../");
		s += 3;
		base = base->parent;
		@@ -88,7 +91,7 @@ static int kernfs_get_target_path(struct kernfs_node *parent,
		if (len < 2)
		return -EINVAL;
		len--;
		if ((s - path) + len > PATH_MAX)
		if ((s - path) + len >= PATH_MAX)
		return -ENAMETOOLONG;

		/* reverse fillup of target string from target to base */

Admin message