From: Bernd Edlinger bernd.edlinger@hotmail.de
[ 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: Bernd Edlinger bernd.edlinger@hotmail.de Acked-by: Tejun Heo tj@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- 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 b3b293e2c0990..0a379a86ff768 100644 --- a/fs/kernfs/symlink.c +++ b/fs/kernfs/symlink.c @@ -63,6 +63,9 @@ 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; @@ -79,7 +82,7 @@ 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 */