diff options
author | Alexei Starovoitov <ast@plumgrid.com> | 2015-08-28 15:56:22 -0700 |
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committer | David S. Miller <davem@davemloft.net> | 2015-08-28 16:27:27 -0700 |
commit | 1a6877b9c0c2ad901d4335d909432d3bb6d3a330 (patch) | |
tree | 25b3a1577a82199d1100834c1bbf6cefad34a5a7 /lib | |
parent | c9fd56b34efd06a031cbc918d288f09e38173ff9 (diff) | |
download | linux-1a6877b9c0c2ad901d4335d909432d3bb6d3a330.tar.bz2 |
lib: introduce strncpy_from_unsafe()
generalize FETCH_FUNC_NAME(memory, string) into
strncpy_from_unsafe() and fix sparse warnings that were
present in original implementation.
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'lib')
-rw-r--r-- | lib/strncpy_from_user.c | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/lib/strncpy_from_user.c b/lib/strncpy_from_user.c index e0af6ff73d14..ead8c4a068d1 100644 --- a/lib/strncpy_from_user.c +++ b/lib/strncpy_from_user.c @@ -112,3 +112,44 @@ long strncpy_from_user(char *dst, const char __user *src, long count) return -EFAULT; } EXPORT_SYMBOL(strncpy_from_user); + +/** + * strncpy_from_unsafe: - Copy a NUL terminated string from unsafe address. + * @dst: Destination address, in kernel space. This buffer must be at + * least @count bytes long. + * @src: Unsafe address. + * @count: Maximum number of bytes to copy, including the trailing NUL. + * + * Copies a NUL-terminated string from unsafe address to kernel buffer. + * + * On success, returns the length of the string INCLUDING the trailing NUL. + * + * If access fails, returns -EFAULT (some data may have been copied + * and the trailing NUL added). + * + * If @count is smaller than the length of the string, copies @count-1 bytes, + * sets the last byte of @dst buffer to NUL and returns @count. + */ +long strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count) +{ + mm_segment_t old_fs = get_fs(); + const void *src = unsafe_addr; + long ret; + + if (unlikely(count <= 0)) + return 0; + + set_fs(KERNEL_DS); + pagefault_disable(); + + do { + ret = __copy_from_user_inatomic(dst++, + (const void __user __force *)src++, 1); + } while (dst[-1] && ret == 0 && src - unsafe_addr < count); + + dst[-1] = '\0'; + pagefault_enable(); + set_fs(old_fs); + + return ret < 0 ? ret : src - unsafe_addr; +} |