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authorAlexei Starovoitov <ast@plumgrid.com>2015-08-28 22:56:22 (GMT)
committerDavid S. Miller <davem@davemloft.net>2015-08-28 23:27:27 (GMT)
commit1a6877b9c0c2ad901d4335d909432d3bb6d3a330 (patch)
tree25b3a1577a82199d1100834c1bbf6cefad34a5a7
parentc9fd56b34efd06a031cbc918d288f09e38173ff9 (diff)
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>
-rw-r--r--include/linux/uaccess.h2
-rw-r--r--kernel/trace/trace_kprobe.c20
-rw-r--r--lib/strncpy_from_user.c41
3 files changed, 47 insertions, 16 deletions
diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index ae572c1..d6f2c2c 100644
--- a/include/linux/uaccess.h
+++ b/include/linux/uaccess.h
@@ -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 strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count);
+
#endif /* __LINUX_UACCESS_H__ */
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index b7d0cdd..c995644 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -165,11 +165,9 @@ DEFINE_BASIC_FETCH_FUNCS(memory)
static void FETCH_FUNC_NAME(memory, string)(struct pt_regs *regs,
void *addr, void *dest)
{
- long ret;
int maxlen = get_rloc_len(*(u32 *)dest);
u8 *dst = get_rloc_data(dest);
- u8 *src = addr;
- mm_segment_t old_fs = get_fs();
+ long ret;
if (!maxlen)
return;
@@ -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
* probing.
*/
- set_fs(KERNEL_DS);
- 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);
+ ret = strncpy_from_unsafe(dst, addr, maxlen);
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));
} else {
- *(u32 *)dest = make_data_rloc(src - (u8 *)addr,
- get_rloc_offs(*(u32 *)dest));
+ *(u32 *)dest = make_data_rloc(ret, get_rloc_offs(*(u32 *)dest));
}
}
NOKPROBE_SYMBOL(FETCH_FUNC_NAME(memory, string));
diff --git a/lib/strncpy_from_user.c b/lib/strncpy_from_user.c
index e0af6ff..ead8c4a 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;
+}

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