@matheusbsbs / matheus-bagliano / commits / 417fb91b5d

compat/win32/syslog: fix use-after-realloc

Git for Windows' SDK recently upgraded to GCC v12.x which points out that the `pos` variable might be used even after the corresponding memory was `realloc()`ed and therefore potentially no longer valid. Since a subset of this SDK is used in Git's CI/PR builds, we need to fix this to continue to be able to benefit from the CI/PR runs. Note: This bug has been with us since 2a6b149c64f6 (mingw: avoid using strbuf in syslog, 2011-10-06), and while it looks tempting to replace the hand-rolled string manipulation with a `strbuf`-based one, that commit's message explains why we cannot do that: The `syslog()` function is called as part of the function in `daemon.c` which is set as the `die()` routine, and since `strbuf_grow()` can call that function if it runs out of memory, this would cause a nasty infinite loop that we do not want to re-introduce. Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Johannes Schindelin committed May 24, 2022 at 00:23 UTC 417fb91b5d193c58a9a31ad6c7901ccfc08ff760

1 file changed +2

compat/win32/syslog.c

@@ -43,6 +43,7 @@ void syslog(int priority, const char *fmt, ...)

43 va_end(ap);

45 while ((pos = strstr(str, "%1")) != NULL) {

46 + size_t offset = pos - str;

47 char *oldstr = str;

48 str = realloc(str, st_add(++str_len, 1));

49 if (!str) {

@@ -50,6 +51,7 @@ void syslog(int priority, const char *fmt, ...)

51 warning_errno("realloc failed");

52 return;

53 }

54 + pos = str + offset;

55 memmove(pos + 2, pos + 1, strlen(pos));

56 pos[1] = ' ';

57 }