commit e2cfd2879a15db00dfa9a42eeb1baaef6a930aff
parent c3b48c6b0bf501802295c85b1cf54275d6b74883
Author: jvoisin <julien.voisin@dustri.org>
Date: Thu, 10 Oct 2024 15:50:40 +0200
Fix a crash in strncpy/stpncpy
```
Core was generated by `scripts/mod/modpost -M -m -o Module.symvers -n -T modules.order vmlinux.o'.
Program terminated with signal SIGSEGV, Segmentation fault.
warning: 17 src/string/strlen.c: No such file or directory
(gdb) bt
```
> I think strncpy logic is broken: `__fh_size_t max_len_s = strlen(__s);` may try read past `size_t __n`.
> Create a buf without any trailing `\0`, do `strncpy(dest, buf, sizeof(buf));`, it should work, since `strncpy` will stop at `sizeof buf`
> but the current fority-headers implementation will do `strlen(buf)`, which will go boom when it is not terminated with \0
Reported-by: ncopa
Diffstat:
8 files changed, 16 insertions(+), 16 deletions(-)
diff --git a/include/string.h b/include/string.h
@@ -208,12 +208,6 @@ _FORTIFY_FN(stpncpy) char *stpncpy(char * _FORTIFY_POS0 __d, const char *__s,
#if __has_builtin(__builtin___stpncpy_chk) && FORTIFY_USE_NATIVE_CHK
return __builtin___stpncpy_chk(__d, __s, __n, __fh_bos(__d, 0));
#else
- __fh_size_t max_len_s = strlen(__s);
- if (max_len_s > __n)
- max_len_s = __n;
- if (__fh_overlap(__d, max_len_s, __s, max_len_s))
- __builtin_trap();
-
// If the length strlen(src) is smaller than n, the remaining
// characters in the array pointed to by dest are filled with null
// bytes ('\0')
@@ -318,12 +312,6 @@ _FORTIFY_FN(strncpy) char *strncpy(char * _FORTIFY_POS0 __d,
#if __has_builtin(__builtin___strncpy_chk) && FORTIFY_USE_NATIVE_CHK
return __builtin___strncpy_chk(__d, __s, __n, __fh_bos(__d, 0));
#else
- __fh_size_t max_len_s = strlen(__s);
- if (max_len_s > __n)
- max_len_s = __n;
- if (__fh_overlap(__d, max_len_s, __s, max_len_s))
- __builtin_trap();
-
// If the length of src is less than n, strncpy() writes additional
// null bytes to dest to ensure that a total of n bytes are written.
__fh_size_t __b = __fh_bos(__d, 0);
diff --git a/tests/test_stpncpy_dynamic_write.c b/tests/test_stpncpy_dynamic_write.c
@@ -3,7 +3,7 @@
#include <string.h>
int main(int argc, char** argv) {
- char buffer[] = {'A', 'B', 'C', 'D', 'E', 'F', '\0'};
+ char buffer[] = {'A', 'B', 'C', 'D', 'E', 'F'};
stpncpy(buffer, "1234567", 3);
puts(buffer);
diff --git a/tests/test_stpncpy_overwrite_over.c b/tests/test_stpncpy_overwrite_over.c
@@ -9,9 +9,11 @@ int main(int argc, char** argv) {
stpncpy(buffer, buffer+5, 2);
puts(buffer);
+#if 0
CHK_FAIL_START
stpncpy(buffer+1, buffer, 5);
CHK_FAIL_END
+#endif
puts(buffer);
return ret;
diff --git a/tests/test_stpncpy_overwrite_under.c b/tests/test_stpncpy_overwrite_under.c
@@ -10,9 +10,11 @@ int main(int argc, char** argv) {
puts(buffer);
char buffer2[] = {'A', 'A', 'A', 'A', 'B', 'B', 'B', 'B', '\0'};
+#if 0
CHK_FAIL_START
stpncpy(buffer2-1, buffer2, 5);
CHK_FAIL_END
+#endif
puts(buffer2);
return ret;
diff --git a/tests/test_strncpy_dynamic_write.c b/tests/test_strncpy_dynamic_write.c
@@ -4,7 +4,9 @@
int main(int argc, char** argv) {
char buffer[8] = {0};
- strncpy(buffer, "1234567", 5);
+ char src[] = {'A', 'B', 'C', 'D', 'E', 'F'};
+
+ strncpy(buffer, src, 5);
puts(buffer);
CHK_FAIL_START
diff --git a/tests/test_strncpy_overwrite_over.c b/tests/test_strncpy_overwrite_over.c
@@ -13,9 +13,11 @@ int main(int argc, char** argv) {
puts(buffer);
char buffer2[9] = {'A', 'A', 'A', 'A', 'B', 'B', 'B', 'B', '\0'};
+#if 0
CHK_FAIL_START
strncpy(buffer2+1, buffer2, 5);
CHK_FAIL_END
+#endif
puts(buffer2);
return ret;
diff --git a/tests/test_strncpy_overwrite_under.c b/tests/test_strncpy_overwrite_under.c
@@ -6,9 +6,11 @@ int main(int argc, char** argv) {
char buffer[9] = {'A', 'A', 'A', 'A', 'B', 'B', 'B', 'B', '\0'};
puts(buffer);
+#if 0
CHK_FAIL_START
strncpy(buffer-1, buffer, 5);
CHK_FAIL_END
+#endif
puts(buffer);
return ret;
diff --git a/tests/test_strncpy_static_write.c b/tests/test_strncpy_static_write.c
@@ -4,11 +4,13 @@
int main(int argc, char** argv) {
char buffer[8] = {0};
- strncpy(buffer, "1234567", 5);
+ char src[] = {'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L'};
+
+ strncpy(buffer, src, 5);
puts(buffer);
CHK_FAIL_START
- strncpy(buffer, "1234567890", 10);
+ strncpy(buffer, src, 10);
CHK_FAIL_END
puts(buffer);
