From 6d6c11977703ca8d75e379107def7336c08a7ca7 Mon Sep 17 00:00:00 2001 From: Walter Doekes Date: Mon, 11 Aug 2014 10:24:06 +0000 Subject: [PATCH] general: Fix memory Corruption in __ast_string_field_ptr_build_va. If the space left in a stringfield is between 0 and (alignof(ast_string_field_allocation)-1) adding new data would cause memory corruption, because we would assume enough space (unsigned underrun). Thanks Arnd Schmitter for reporting and finding out the cause! ASTERISK-23508 #close Reported by: Arnd Schmitter Tested by: Arnd Schmitter, JoshE Review: https://reviewboard.asterisk.org/r/3898/ git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.8@420680 65c4cc65-6c06-0410-ace0-fbb531ad65f3 --- main/utils.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-) diff --git a/main/utils.c b/main/utils.c index 93c1f1bf82..1bb6e76a46 100644 --- a/main/utils.c +++ b/main/utils.c @@ -1913,6 +1913,7 @@ void __ast_string_field_ptr_build_va(struct ast_string_field_mgr *mgr, size_t needed; size_t available; size_t space = (*pool_head)->size - (*pool_head)->used; + int res; ssize_t grow; char *target; @@ -1931,10 +1932,19 @@ void __ast_string_field_ptr_build_va(struct ast_string_field_mgr *mgr, * so we don't need to re-align anything here. */ target = (*pool_head)->base + (*pool_head)->used + ast_alignof(ast_string_field_allocation); - available = space - ast_alignof(ast_string_field_allocation); + if (space > ast_alignof(ast_string_field_allocation)) { + available = space - ast_alignof(ast_string_field_allocation); + } else { + available = 0; + } } - needed = vsnprintf(target, available, format, ap1) + 1; + res = vsnprintf(target, available, format, ap1); + if (res < 0) { + /* Are we out of memory? */ + return; + } + needed = (size_t)res + 1; /* NUL byte */ if (needed > available) { /* the allocation could not be satisfied using the field's current allocation @@ -1953,7 +1963,8 @@ void __ast_string_field_ptr_build_va(struct ast_string_field_mgr *mgr, */ __ast_string_field_release_active(*pool_head, *ptr); mgr->last_alloc = *ptr = target; - AST_STRING_FIELD_ALLOCATION(target) = needed; + ast_assert(needed < (ast_string_field_allocation)-1); + AST_STRING_FIELD_ALLOCATION(target) = (ast_string_field_allocation)needed; (*pool_head)->used += ast_make_room_for(needed, ast_string_field_allocation); (*pool_head)->active += needed; } else if ((grow = (needed - AST_STRING_FIELD_ALLOCATION(*ptr))) > 0) {