diff options
author | Sean Paul <seanpaul@chromium.org> | 2019-10-23 11:14:11 -0400 |
---|---|---|
committer | Sean Paul <seanpaul@chromium.org> | 2019-10-23 11:14:11 -0400 |
commit | 44bf67f32a6803339ac1ba721b158c3e2272cabe (patch) | |
tree | 1ed93503a4a1d20005b85df91bd81e5f5982f348 /lib/usercopy.c | |
parent | a96bf3cbd7b8557f5c5c7938e5f8926ea39d55e9 (diff) | |
parent | 2e79e22e092acd55da0b2db066e4826d7d152c41 (diff) | |
download | linux-44bf67f32a6803339ac1ba721b158c3e2272cabe.tar.gz |
Merge drm/drm-next into drm-misc-next
Parroting Daniel's backmerge justification from
2e79e22e092acd55da0b2db066e4826d7d152c41:
Thierry needs fd70c7755bf0 ("drm/bridge: tc358767: fix max_tu_symbol
value") to be able to merge his dp_link patch series.
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Diffstat (limited to 'lib/usercopy.c')
-rw-r--r-- | lib/usercopy.c | 55 |
1 files changed, 55 insertions, 0 deletions
diff --git a/lib/usercopy.c b/lib/usercopy.c index c2bfbcaeb3dc..cbb4d9ec00f2 100644 --- a/lib/usercopy.c +++ b/lib/usercopy.c @@ -1,5 +1,6 @@ // SPDX-License-Identifier: GPL-2.0 #include <linux/uaccess.h> +#include <linux/bitops.h> /* out-of-line parts */ @@ -31,3 +32,57 @@ unsigned long _copy_to_user(void __user *to, const void *from, unsigned long n) } EXPORT_SYMBOL(_copy_to_user); #endif + +/** + * check_zeroed_user: check if a userspace buffer only contains zero bytes + * @from: Source address, in userspace. + * @size: Size of buffer. + * + * This is effectively shorthand for "memchr_inv(from, 0, size) == NULL" for + * userspace addresses (and is more efficient because we don't care where the + * first non-zero byte is). + * + * Returns: + * * 0: There were non-zero bytes present in the buffer. + * * 1: The buffer was full of zero bytes. + * * -EFAULT: access to userspace failed. + */ +int check_zeroed_user(const void __user *from, size_t size) +{ + unsigned long val; + uintptr_t align = (uintptr_t) from % sizeof(unsigned long); + + if (unlikely(size == 0)) + return 1; + + from -= align; + size += align; + + if (!user_access_begin(from, size)) + return -EFAULT; + + unsafe_get_user(val, (unsigned long __user *) from, err_fault); + if (align) + val &= ~aligned_byte_mask(align); + + while (size > sizeof(unsigned long)) { + if (unlikely(val)) + goto done; + + from += sizeof(unsigned long); + size -= sizeof(unsigned long); + + unsafe_get_user(val, (unsigned long __user *) from, err_fault); + } + + if (size < sizeof(unsigned long)) + val &= aligned_byte_mask(size); + +done: + user_access_end(); + return (val == 0); +err_fault: + user_access_end(); + return -EFAULT; +} +EXPORT_SYMBOL(check_zeroed_user); |