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| author | Christophe Leroy <christophe.leroy@c-s.fr> | 2020-01-23 08:34:18 +0000 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-01-24 09:27:34 -0800 |
| commit | ab10ae1c3bef56c29bac61e1201c752221b87b41 (patch) | |
| tree | 20ae31e0a7fcbbbe516fbba8aeacf43c0ea37205 /lib/strncpy_from_user.c | |
| parent | 838a860a390547dc6f8bc9d0a77d4ebad1dc8ff1 (diff) | |
| download | linux-ab10ae1c3bef56c29bac61e1201c752221b87b41.tar.bz2 | |
lib: Reduce user_access_begin() boundaries in strncpy_from_user() and strnlen_user()
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>
Diffstat (limited to 'lib/strncpy_from_user.c')
| -rw-r--r-- | lib/strncpy_from_user.c | 14 |
1 files changed, 7 insertions, 7 deletions
diff --git a/lib/strncpy_from_user.c b/lib/strncpy_from_user.c index dccb95af6003..706020b06617 100644 --- a/lib/strncpy_from_user.c +++ b/lib/strncpy_from_user.c @@ -30,13 +30,6 @@ static inline long do_strncpy_from_user(char *dst, const char __user *src, 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 char __user *src, long count) 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)) { |