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From 0ccea50c697512b4bcbe76780260dfba09450327 Mon Sep 17 00:00:00 2001
From: Rich Felker <dalias@aerifal.cx>
Date: Wed, 10 Jul 2013 14:38:20 -0400
Subject: [PATCH 07/10] fix invalid library phdr pointers passed to callback
from dl_iterate_phdr
map_library was saving pointers to an automatic-storage buffer rather
than pointers into the mapping. this should be a fairly simple fix,
but the patch here is slightly complicated by two issues:
1. supporting gratuitously obfuscated ELF files where the program
headers are not right at the beginning of the file.
2. cleaning up the map_library function so that data isn't clobbered
by the time we need it.
---
src/ldso/dynlink.c | 25 ++++++++++++++++---------
1 file changed, 16 insertions(+), 9 deletions(-)
diff --git a/src/ldso/dynlink.c b/src/ldso/dynlink.c
index 7031d03..ff5b738 100644
--- a/src/ldso/dynlink.c
+++ b/src/ldso/dynlink.c
@@ -309,7 +309,7 @@ static void *map_library(int fd, struct dso *dso)
size_t this_min, this_max;
off_t off_start;
Ehdr *eh;
- Phdr *ph;
+ Phdr *ph, *ph0;
unsigned prot;
unsigned char *map, *base;
size_t dyn;
@@ -324,11 +324,10 @@ static void *map_library(int fd, struct dso *dso)
if (eh->e_phoff + phsize > l) {
l = pread(fd, buf+1, phsize, eh->e_phoff);
if (l != phsize) return 0;
- eh->e_phoff = sizeof *eh;
+ ph = ph0 = (void *)(buf + 1);
+ } else {
+ ph = ph0 = (void *)((char *)buf + eh->e_phoff);
}
- ph = (void *)((char *)buf + eh->e_phoff);
- dso->phdr = ph;
- dso->phnum = eh->e_phnum;
for (i=eh->e_phnum; i; i--, ph=(void *)((char *)ph+eh->e_phentsize)) {
if (ph->p_type == PT_DYNAMIC)
dyn = ph->p_vaddr;
@@ -363,9 +362,18 @@ static void *map_library(int fd, struct dso *dso)
map = mmap((void *)addr_min, map_len, prot, MAP_PRIVATE, fd, off_start);
if (map==MAP_FAILED) return 0;
base = map - addr_min;
- ph = (void *)((char *)buf + eh->e_phoff);
- for (i=eh->e_phnum; i; i--, ph=(void *)((char *)ph+eh->e_phentsize)) {
+ dso->phdr = 0;
+ dso->phnum = 0;
+ for (ph=ph0, i=eh->e_phnum; i; i--, ph=(void *)((char *)ph+eh->e_phentsize)) {
if (ph->p_type != PT_LOAD) continue;
+ /* Check if the programs headers are in this load segment, and
+ * if so, record the address for use by dl_iterate_phdr. */
+ if (!dso->phdr && eh->e_phoff >= ph->p_offset
+ && eh->e_phoff+phsize <= ph->p_offset+ph->p_filesz) {
+ dso->phdr = (void *)(base + ph->p_vaddr
+ + (eh->e_phoff-ph->p_offset));
+ dso->phnum = eh->e_phnum;
+ }
/* Reuse the existing mapping for the lowest-address LOAD */
if ((ph->p_vaddr & -PAGE_SIZE) == addr_min) continue;
this_min = ph->p_vaddr & -PAGE_SIZE;
@@ -390,8 +398,7 @@ static void *map_library(int fd, struct dso *dso)
goto error;
break;
}
- if (!runtime) reclaim_gaps(base, (void *)((char *)buf + eh->e_phoff),
- eh->e_phentsize, eh->e_phnum);
+ if (!runtime) reclaim_gaps(base, ph0, eh->e_phentsize, eh->e_phnum);
dso->map = map;
dso->map_len = map_len;
dso->base = base;
--
1.8.3.2
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