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author | Alexei Starovoitov <ast@plumgrid.com> | 2015-08-28 15:56:22 -0700 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2015-08-28 16:27:27 -0700 |
commit | 1a6877b9c0c2ad901d4335d909432d3bb6d3a330 (patch) | |
tree | 25b3a1577a82199d1100834c1bbf6cefad34a5a7 | |
parent | c9fd56b34efd06a031cbc918d288f09e38173ff9 (diff) | |
download | op-kernel-dev-1a6877b9c0c2ad901d4335d909432d3bb6d3a330.zip op-kernel-dev-1a6877b9c0c2ad901d4335d909432d3bb6d3a330.tar.gz |
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.h | 2 | ||||
-rw-r--r-- | kernel/trace/trace_kprobe.c | 20 | ||||
-rw-r--r-- | lib/strncpy_from_user.c | 41 |
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; +} |