From: Jan Kara <jack@xxxxxxx> [ Upstream commit f18c34e483ff6b1d9866472221e4015b3a4698e4 ] If the specified maximum length of the string is a multiple of unsigned long, we would load one long behind the specified maximum. If that happens to be in a next page, we can hit a page fault although we were not expected to. Fix the off-by-one bug in the test whether we are at the end of the specified range. Signed-off-by: Jan Kara <jack@xxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sasha.levin@xxxxxxxxxx> --- lib/strnlen_user.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/lib/strnlen_user.c b/lib/strnlen_user.c index a28df52..1164961 100644 --- a/lib/strnlen_user.c +++ b/lib/strnlen_user.c @@ -57,7 +57,8 @@ static inline long do_strnlen_user(const char __user *src, unsigned long count, return res + find_zero(data) + 1 - align; } res += sizeof(unsigned long); - if (unlikely(max < sizeof(unsigned long))) + /* We already handled 'unsigned long' bytes. Did we do it all ? */ + if (unlikely(max <= sizeof(unsigned long))) break; max -= sizeof(unsigned long); if (unlikely(__get_user(c,(unsigned long __user *)(src+res)))) -- 2.1.0 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html