diff options
author | Ingo Molnar <mingo@kernel.org> | 2019-11-11 08:34:59 +0100 |
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committer | Ingo Molnar <mingo@kernel.org> | 2019-11-11 08:34:59 +0100 |
commit | 6d5a763c303bc9d78b17361d30b692ba2facf9b4 (patch) | |
tree | 1ba7059e8b1c47eb075acc906f8ef01f9c490ba1 /lib/usercopy.c | |
parent | e79b3ddad6790aabead5fb775456a5b0599e97ee (diff) | |
parent | 31f4f5b495a62c9a8b15b1c3581acd5efeb9af8c (diff) |
Merge tag 'v5.4-rc7' into sched/core, to pick up fixes
Signed-off-by: Ingo Molnar <mingo@kernel.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); |