From: Phil Pennock Date: Fri, 30 Oct 2020 00:49:49 +0000 (-0400) Subject: SECURITY: refuse too small store allocations X-Git-Tag: exim-4.95-RC0~51^2~44 X-Git-Url: https://git.exim.org/exim.git/commitdiff_plain/15282ddb92382fb203e61d7a66f37aa2fbdebb82 SECURITY: refuse too small store allocations Negative sizes are definitely bad. Optimistically, I'm saying that zero is bad too. But perhaps we have something doing that, expecting to be able to grow. In which case we'll have to amend this. (cherry picked from commit 1c9afcec0043e2fb72607b2addb0613763705549) (cherry picked from commit 6f5d7e5af8eff688c36f81334e4f063689561963) --- diff --git a/doc/doc-txt/ChangeLog b/doc/doc-txt/ChangeLog index 95b95e794..5a9c8f214 100644 --- a/doc/doc-txt/ChangeLog +++ b/doc/doc-txt/ChangeLog @@ -273,8 +273,10 @@ PP/05 Fix security issue CVE-2020-PFPSN and guard against cmdline invoker providing a particularly obnoxious sender full name. Reported by Qualys. -pp/06 Fix CVE-2020-28016 (PFPZA): Heap out-of-bounds write in parse_fix_phrase() +PP/06 Fix CVE-2020-28016 (PFPZA): Heap out-of-bounds write in parse_fix_phrase() +PP/07 Refuse to allocate too little memory, block negative/zero allocations. + Security guard. Exim version 4.94 diff --git a/src/src/store.c b/src/src/store.c index 22615ea08..b5115fa13 100644 --- a/src/src/store.c +++ b/src/src/store.c @@ -268,6 +268,17 @@ store_get_3(int size, BOOL tainted, const char *func, int linenumber) { int pool = tainted ? store_pool + POOL_TAINT_BASE : store_pool; +/* Ensure we've been asked to allocate memory. +A negative size is a sign of a security problem. +A zero size is also suspect (but we might have to allow it if we find our API +expects it in some places). */ +if (size < 1) + { + log_write(0, LOG_MAIN|LOG_PANIC_DIE, + "bad memory allocation requested (%d bytes) at %s %d", + size, func, linenumber); + } + /* Round up the size to a multiple of the alignment. Although this looks a messy statement, because "alignment" is a constant expression, the compiler can do a reasonable job of optimizing, especially if the value of "alignment" is a