From fead7e3fc04729b4cc8a5feec4a172b389395212 Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Wed, 28 Oct 2015 21:45:31 -0400 Subject: [PATCH] fix missing bss handling in FDPIC ELF loader when a library being loaded has bss (i.e. data segment with p_memsz>p_filesz), this region needs to be zeroed with a combination of memset and/or mmap. the regular ELF loader always did this but the FDPIC code path omitted it, leading to objects in bss having uninitialized/junk contents. --- src/ldso/dynlink.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/src/ldso/dynlink.c b/src/ldso/dynlink.c index 642ecc30..a6484dd5 100644 --- a/src/ldso/dynlink.c +++ b/src/ldso/dynlink.c @@ -604,6 +604,19 @@ static void *map_library(int fd, struct dso *dso) dso->loadmap->segs[i].p_vaddr = ph->p_vaddr; dso->loadmap->segs[i].p_memsz = ph->p_memsz; i++; + if (prot & PROT_WRITE) { + size_t brk = (ph->p_vaddr & PAGE_SIZE-1) + + ph->p_filesz; + size_t pgbrk = brk + PAGE_SIZE-1 & -PAGE_SIZE; + size_t pgend = brk + ph->p_memsz - ph->p_filesz + + PAGE_SIZE-1 & -PAGE_SIZE; + if (pgend > pgbrk && mmap_fixed(map+pgbrk, + pgend-pgbrk, prot, + MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, + -1, off_start) == MAP_FAILED) + goto error; + memset(map + brk, 0, pgbrk-brk); + } } map = (void *)dso->loadmap->segs[0].addr; map_len = 0;