Fix CVE-2017-16943: https://bugs.exim.org/show_bug.cgi?id=2199 https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-16943 Patch copied from upstream source repository: https://git.exim.org/exim.git/commit/4090d62a4b25782129cc1643596dc2f6e8f63bde From 4090d62a4b25782129cc1643596dc2f6e8f63bde Mon Sep 17 00:00:00 2001 From: Jeremy Harris Date: Fri, 24 Nov 2017 20:22:33 +0000 Subject: [PATCH] Avoid release of store if there have been later allocations. Bug 2199 --- doc/doc-txt/ChangeLog | 4 ++++ src/src/receive.c | 7 ++++--- 2 files changed, 8 insertions(+), 3 deletions(-) #diff --git a/doc/doc-txt/ChangeLog b/doc/doc-txt/ChangeLog #index e937ba2..a2d9339 100644 #--- a/doc/doc-txt/ChangeLog #+++ b/doc/doc-txt/ChangeLog #@@ -59,6 +59,10 @@ JH/30 Fix a logging bug on aarch64: an unsafe routine was previously used for # connection in response to HELO" was logged instead of the actual 4xx # error for the HELO. # #+JH/34 Bug 2199: fix a use-after-free while reading smtp input for header lines. #+ A crafted sequence of BDAT commands could result in in-use memory beeing #+ freed. #+ # Exim version 4.89 ----------------- diff --git a/src/src/receive.c b/src/src/receive.c index 95cf13e..20672db 100644 --- a/src/receive.c +++ b/src/receive.c @@ -1772,8 +1772,8 @@ for (;;) (and sometimes lunatic messages can have ones that are 100s of K long) we call store_release() for strings that have been copied - if the string is at the start of a block (and therefore the only thing in it, because we aren't - doing any other gets), the block gets freed. We can only do this because we - know there are no other calls to store_get() going on. */ + doing any other gets), the block gets freed. We can only do this release if + there were no allocations since the once that we want to free. */ if (ptr >= header_size - 4) { @@ -1782,9 +1782,10 @@ for (;;) header_size *= 2; if (!store_extend(next->text, oldsize, header_size)) { + BOOL release_ok = store_last_get[store_pool] == next->text; uschar *newtext = store_get(header_size); memcpy(newtext, next->text, ptr); - store_release(next->text); + if (release_ok) store_release(next->text); next->text = newtext; } } -- 1.9.1