From: Christophe Leroy christophe.leroy@c-s.fr
commit ab10ae1c3bef56c29bac61e1201c752221b87b41 upstream.
The range passed to user_access_begin() by strncpy_from_user() and strnlen_user() starts at 'src' and goes up to the limit of userspace although reads will be limited by the 'count' param.
On 32 bits powerpc (book3s/32) access has to be granted for each 256Mbytes segment and the cost increases with the number of segments to unlock.
Limit the range with 'count' param.
Fixes: 594cc251fdd0 ("make 'user_access_begin()' do 'access_ok()'") Signed-off-by: Christophe Leroy christophe.leroy@c-s.fr Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- lib/strncpy_from_user.c | 14 +++++++------- lib/strnlen_user.c | 14 +++++++------- 2 files changed, 14 insertions(+), 14 deletions(-)
--- a/lib/strncpy_from_user.c +++ b/lib/strncpy_from_user.c @@ -30,13 +30,6 @@ static inline long do_strncpy_from_user( const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS; unsigned long res = 0;
- /* - * Truncate 'max' to the user-specified limit, so that - * we only have one limit we need to check in the loop - */ - if (max > count) - max = count; - if (IS_UNALIGNED(src, dst)) goto byte_at_a_time;
@@ -114,6 +107,13 @@ long strncpy_from_user(char *dst, const unsigned long max = max_addr - src_addr; long retval;
+ /* + * Truncate 'max' to the user-specified limit, so that + * we only have one limit we need to check in the loop + */ + if (max > count) + max = count; + kasan_check_write(dst, count); check_object_size(dst, count, false); if (user_access_begin(src, max)) { --- a/lib/strnlen_user.c +++ b/lib/strnlen_user.c @@ -27,13 +27,6 @@ static inline long do_strnlen_user(const unsigned long c;
/* - * Truncate 'max' to the user-specified limit, so that - * we only have one limit we need to check in the loop - */ - if (max > count) - max = count; - - /* * Do everything aligned. But that means that we * need to also expand the maximum.. */ @@ -109,6 +102,13 @@ long strnlen_user(const char __user *str unsigned long max = max_addr - src_addr; long retval;
+ /* + * Truncate 'max' to the user-specified limit, so that + * we only have one limit we need to check in the loop + */ + if (max > count) + max = count; + if (user_access_begin(str, max)) { retval = do_strnlen_user(str, count, max); user_access_end();