Commit | Line | Data |
---|---|---|
c33fa9f5 IM |
1 | /* |
2 | * Access kernel memory without faulting. | |
3 | */ | |
b95f1b31 | 4 | #include <linux/export.h> |
c33fa9f5 | 5 | #include <linux/mm.h> |
7c7fcf76 | 6 | #include <linux/uaccess.h> |
c33fa9f5 IM |
7 | |
8 | /** | |
9 | * probe_kernel_read(): safely attempt to read from a location | |
10 | * @dst: pointer to the buffer that shall take the data | |
11 | * @src: address to read from | |
12 | * @size: size of the data chunk | |
13 | * | |
14 | * Safely read from address @src to the buffer at @dst. If a kernel fault | |
15 | * happens, handle that and return -EFAULT. | |
16 | */ | |
6144a85a | 17 | |
f29c5041 | 18 | long __weak probe_kernel_read(void *dst, const void *src, size_t size) |
6144a85a JW |
19 | __attribute__((alias("__probe_kernel_read"))); |
20 | ||
f29c5041 | 21 | long __probe_kernel_read(void *dst, const void *src, size_t size) |
c33fa9f5 IM |
22 | { |
23 | long ret; | |
b4b8ac52 | 24 | mm_segment_t old_fs = get_fs(); |
c33fa9f5 | 25 | |
b4b8ac52 | 26 | set_fs(KERNEL_DS); |
c33fa9f5 IM |
27 | pagefault_disable(); |
28 | ret = __copy_from_user_inatomic(dst, | |
29 | (__force const void __user *)src, size); | |
30 | pagefault_enable(); | |
b4b8ac52 | 31 | set_fs(old_fs); |
c33fa9f5 IM |
32 | |
33 | return ret ? -EFAULT : 0; | |
34 | } | |
35 | EXPORT_SYMBOL_GPL(probe_kernel_read); | |
36 | ||
37 | /** | |
38 | * probe_kernel_write(): safely attempt to write to a location | |
39 | * @dst: address to write to | |
40 | * @src: pointer to the data that shall be written | |
41 | * @size: size of the data chunk | |
42 | * | |
43 | * Safely write to address @dst from the buffer at @src. If a kernel fault | |
44 | * happens, handle that and return -EFAULT. | |
45 | */ | |
f29c5041 | 46 | long __weak probe_kernel_write(void *dst, const void *src, size_t size) |
6144a85a JW |
47 | __attribute__((alias("__probe_kernel_write"))); |
48 | ||
f29c5041 | 49 | long __probe_kernel_write(void *dst, const void *src, size_t size) |
c33fa9f5 IM |
50 | { |
51 | long ret; | |
b4b8ac52 | 52 | mm_segment_t old_fs = get_fs(); |
c33fa9f5 | 53 | |
b4b8ac52 | 54 | set_fs(KERNEL_DS); |
c33fa9f5 IM |
55 | pagefault_disable(); |
56 | ret = __copy_to_user_inatomic((__force void __user *)dst, src, size); | |
57 | pagefault_enable(); | |
b4b8ac52 | 58 | set_fs(old_fs); |
c33fa9f5 IM |
59 | |
60 | return ret ? -EFAULT : 0; | |
61 | } | |
62 | EXPORT_SYMBOL_GPL(probe_kernel_write); | |
dbb7ee0e AS |
63 | |
64 | /** | |
65 | * strncpy_from_unsafe: - Copy a NUL terminated string from unsafe address. | |
66 | * @dst: Destination address, in kernel space. This buffer must be at | |
67 | * least @count bytes long. | |
68 | * @src: Unsafe address. | |
69 | * @count: Maximum number of bytes to copy, including the trailing NUL. | |
70 | * | |
71 | * Copies a NUL-terminated string from unsafe address to kernel buffer. | |
72 | * | |
73 | * On success, returns the length of the string INCLUDING the trailing NUL. | |
74 | * | |
75 | * If access fails, returns -EFAULT (some data may have been copied | |
76 | * and the trailing NUL added). | |
77 | * | |
78 | * If @count is smaller than the length of the string, copies @count-1 bytes, | |
79 | * sets the last byte of @dst buffer to NUL and returns @count. | |
80 | */ | |
81 | long strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count) | |
82 | { | |
83 | mm_segment_t old_fs = get_fs(); | |
84 | const void *src = unsafe_addr; | |
85 | long ret; | |
86 | ||
87 | if (unlikely(count <= 0)) | |
88 | return 0; | |
89 | ||
90 | set_fs(KERNEL_DS); | |
91 | pagefault_disable(); | |
92 | ||
93 | do { | |
94 | ret = __copy_from_user_inatomic(dst++, | |
95 | (const void __user __force *)src++, 1); | |
96 | } while (dst[-1] && ret == 0 && src - unsafe_addr < count); | |
97 | ||
98 | dst[-1] = '\0'; | |
99 | pagefault_enable(); | |
100 | set_fs(old_fs); | |
101 | ||
102 | return ret < 0 ? ret : src - unsafe_addr; | |
103 | } |