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authorJan Kara <jack@suse.cz>2015-06-02 17:10:28 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2015-06-05 23:19:54 -0700
commit73f668104f25d364f758e8c6738c2a1826d2f0fc (patch)
tree2bdd39a64fab484ca22b66d2395a35eb4179e20c /lib
parente9aba80e289b3491597422f1bf843be5e8099a2d (diff)
lib: Fix strnlen_user() to not touch memory after specified maximum
commit f18c34e483ff6b1d9866472221e4015b3a4698e4 upstream. 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@suse.cz> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'lib')
-rw-r--r--lib/strnlen_user.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/lib/strnlen_user.c b/lib/strnlen_user.c
index a28df5206d95..11649615c505 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))))