From a75e78f21f9ad4b810868c89dbbabcc3931591ca Mon Sep 17 00:00:00 2001
From: Bernd Edlinger <bernd.edlinger@hotmail.de>
Date: Sat, 7 Jul 2018 17:52:47 +0000
Subject: [PATCH] kernfs: Fix range checks in kernfs_get_target_path
Git-commit: a75e78f21f9ad4b810868c89dbbabcc3931591ca
Patch-mainline: v4.20-rc1
References: bsc#1051510
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>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
fs/kernfs/symlink.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/fs/kernfs/symlink.c b/fs/kernfs/symlink.c
index 305b220af45d..162f43b80c84 100644
--- a/fs/kernfs/symlink.c
+++ b/fs/kernfs/symlink.c
@@ -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 */
--
2.16.4