From 42eedb04c1ad71548043c33ef1996dfe8e524996 Mon Sep 17 00:00:00 2001 From: Michael Brown Date: Mon, 4 Sep 2017 14:00:32 +0100 Subject: [PATCH] [malloc] Avoid false positive warnings from valgrind Calling discard_cache() is likely to result in a call to free_memblock(), which will call valgrind_make_blocks_noaccess() before returning. This causes valgrind to report an invalid read on the next iteration through the loop in alloc_memblock(). Fix by explicitly calling valgrind_make_blocks_defined() after discard_cache() returns. Also call valgrind_make_blocks_noaccess() before calling discard_cache(), to guard against free list corruption while executing cache discarders. Signed-off-by: Michael Brown --- src/core/malloc.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/src/core/malloc.c b/src/core/malloc.c index 6ddc08b7..91c8e4d3 100644 --- a/src/core/malloc.c +++ b/src/core/malloc.c @@ -284,6 +284,7 @@ void * alloc_memblock ( size_t size, size_t align, size_t offset ) { size_t post_size; struct memory_block *pre; struct memory_block *post; + unsigned int discarded; void *ptr; /* Sanity checks */ @@ -371,7 +372,13 @@ void * alloc_memblock ( size_t size, size_t align, size_t offset ) { } /* Try discarding some cached data to free up memory */ - if ( ! discard_cache() ) { + DBGC ( &heap, "Attempting discard for %#zx (aligned %#zx+%zx), " + "used %zdkB\n", size, align, offset, ( usedmem >> 10 ) ); + valgrind_make_blocks_noaccess(); + discarded = discard_cache(); + valgrind_make_blocks_defined(); + check_blocks(); + if ( ! discarded ) { /* Nothing available to discard */ DBGC ( &heap, "Failed to allocate %#zx (aligned " "%#zx)\n", size, align );