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Commit ada2a0f1 authored by Bernd Edlinger's avatar Bernd Edlinger Committed by Greg Kroah-Hartman
Browse files

kernfs: Fix range checks in kernfs_get_target_path 



[ Upstream commit a75e78f21f9ad4b810868c89dbbabcc3931591ca ]

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: default avatarBernd Edlinger <bernd.edlinger@hotmail.de>
Acked-by: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 5fba8151

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 */