Commit cc7acad1 authored by David S. Miller's avatar David S. Miller

Merge branch 'bpf_trace_printk-percent-s'

Alexei Starovoitov says:

====================
support for '%s' in bpf_trace_printk

v2->v3:
fix the comment to mention that strncpy_from_unsafe() returns
the length of the string including the trailing NUL.

v1->v2:
patch 1: generalize FETCH_FUNC_NAME(memory, string) into
strncpy_from_unsafe()
patch 2: use it in bpf_trace_printk
====================
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parents c9fd56b3 8d3b7dce
......@@ -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__ */
......@@ -81,13 +81,16 @@ static const struct bpf_func_proto bpf_probe_read_proto = {
/*
* limited trace_printk()
* only %d %u %x %ld %lu %lx %lld %llu %llx %p conversion specifiers allowed
* only %d %u %x %ld %lu %lx %lld %llu %llx %p %s conversion specifiers allowed
*/
static u64 bpf_trace_printk(u64 r1, u64 fmt_size, u64 r3, u64 r4, u64 r5)
{
char *fmt = (char *) (long) r1;
bool str_seen = false;
int mod[3] = {};
int fmt_cnt = 0;
u64 unsafe_addr;
char buf[64];
int i;
/*
......@@ -114,12 +117,37 @@ static u64 bpf_trace_printk(u64 r1, u64 fmt_size, u64 r3, u64 r4, u64 r5)
if (fmt[i] == 'l') {
mod[fmt_cnt]++;
i++;
} else if (fmt[i] == 'p') {
} else if (fmt[i] == 'p' || fmt[i] == 's') {
mod[fmt_cnt]++;
i++;
if (!isspace(fmt[i]) && !ispunct(fmt[i]) && fmt[i] != 0)
return -EINVAL;
fmt_cnt++;
if (fmt[i - 1] == 's') {
if (str_seen)
/* allow only one '%s' per fmt string */
return -EINVAL;
str_seen = true;
switch (fmt_cnt) {
case 1:
unsafe_addr = r3;
r3 = (long) buf;
break;
case 2:
unsafe_addr = r4;
r4 = (long) buf;
break;
case 3:
unsafe_addr = r5;
r5 = (long) buf;
break;
}
buf[0] = 0;
strncpy_from_unsafe(buf,
(void *) (long) unsafe_addr,
sizeof(buf));
}
continue;
}
......
......@@ -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));
......
......@@ -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;
}
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment