Commit 1a6877b9 authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by David S. Miller

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: default avatarAlexei Starovoitov <ast@plumgrid.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent c9fd56b3
...@@ -129,4 +129,6 @@ extern long __probe_kernel_read(void *dst, const void *src, size_t size); ...@@ -129,4 +129,6 @@ extern long __probe_kernel_read(void *dst, const void *src, size_t size);
extern long notrace probe_kernel_write(void *dst, const void *src, size_t size); extern long notrace probe_kernel_write(void *dst, const void *src, size_t size);
extern long notrace __probe_kernel_write(void *dst, const void *src, size_t size); extern long notrace __probe_kernel_write(void *dst, const void *src, size_t size);
extern long strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count);
#endif /* __LINUX_UACCESS_H__ */ #endif /* __LINUX_UACCESS_H__ */
...@@ -165,11 +165,9 @@ DEFINE_BASIC_FETCH_FUNCS(memory) ...@@ -165,11 +165,9 @@ DEFINE_BASIC_FETCH_FUNCS(memory)
static void FETCH_FUNC_NAME(memory, string)(struct pt_regs *regs, static void FETCH_FUNC_NAME(memory, string)(struct pt_regs *regs,
void *addr, void *dest) void *addr, void *dest)
{ {
long ret;
int maxlen = get_rloc_len(*(u32 *)dest); int maxlen = get_rloc_len(*(u32 *)dest);
u8 *dst = get_rloc_data(dest); u8 *dst = get_rloc_data(dest);
u8 *src = addr; long ret;
mm_segment_t old_fs = get_fs();
if (!maxlen) if (!maxlen)
return; return;
...@@ -178,23 +176,13 @@ static void FETCH_FUNC_NAME(memory, string)(struct pt_regs *regs, ...@@ -178,23 +176,13 @@ static void FETCH_FUNC_NAME(memory, string)(struct pt_regs *regs,
* Try to get string again, since the string can be changed while * Try to get string again, since the string can be changed while
* probing. * probing.
*/ */
set_fs(KERNEL_DS); ret = strncpy_from_unsafe(dst, addr, maxlen);
pagefault_disable();
do
ret = __copy_from_user_inatomic(dst++, src++, 1);
while (dst[-1] && ret == 0 && src - (u8 *)addr < maxlen);
dst[-1] = '\0';
pagefault_enable();
set_fs(old_fs);
if (ret < 0) { /* Failed to fetch string */ if (ret < 0) { /* Failed to fetch string */
((u8 *)get_rloc_data(dest))[0] = '\0'; dst[0] = '\0';
*(u32 *)dest = make_data_rloc(0, get_rloc_offs(*(u32 *)dest)); *(u32 *)dest = make_data_rloc(0, get_rloc_offs(*(u32 *)dest));
} else { } else {
*(u32 *)dest = make_data_rloc(src - (u8 *)addr, *(u32 *)dest = make_data_rloc(ret, get_rloc_offs(*(u32 *)dest));
get_rloc_offs(*(u32 *)dest));
} }
} }
NOKPROBE_SYMBOL(FETCH_FUNC_NAME(memory, string)); NOKPROBE_SYMBOL(FETCH_FUNC_NAME(memory, string));
......
...@@ -112,3 +112,44 @@ long strncpy_from_user(char *dst, const char __user *src, long count) ...@@ -112,3 +112,44 @@ long strncpy_from_user(char *dst, const char __user *src, long count)
return -EFAULT; return -EFAULT;
} }
EXPORT_SYMBOL(strncpy_from_user); 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;
}
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