Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

uprobe: avoid out-of-bounds memory access of fetching args

Uprobe needs to fetch args into a percpu buffer, and then copy to ring buffer to avoid non-atomic context problem.

Sometimes user-space strings, arrays can be very large, but the size of percpu buffer is only page size. And store_trace_args() won't check whether these data exceeds a single page or not, caused out-of-bounds memory access.

It could be reproduced by following steps: 1. build kernel with CONFIG_KASAN enabled 2. save follow program as test.c

``` \#include <stdio.h> \#include <stdlib.h> \#include <string.h>

// If string length large than MAX_STRING_SIZE, the fetch_store_strlen() // will return 0, cause __get_data_size() return shorter size, and // store_trace_args() will not trigger out-of-bounds access. // So make string length less than 4096. \#define STRLEN 4093

void generate_string(char *str, int n) { int i; for (i = 0; i < n; ++i) { char c = i % 26 + 'a'; str[i] = c; } str[n-1] = '\0'; }

void print_string(char *str) { printf("%s\n", str); }

int main() { char tmp[STRLEN];

generate_string(tmp, STRLEN); print_string(tmp);

return 0; } ``` 3. compile program `gcc -o test test.c`

4. get the offset of `print_string()` ``` objdump -t test | grep -w print_string 0000000000401199 g F .text 000000000000001b print_string ```

5. configure uprobe with offset 0x11…