musl - musl - an implementation of the standard library for Linux-based systems

musl - an implementation of the standard library for Linux-based systems

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author	Rich Felker <dalias@aerifal.cx>	2017年07月04日 10:58:13 -0400
committer	Rich Felker <dalias@aerifal.cx>	2017年07月04日 11:05:05 -0400
commit	66b53cfa8876342f7e7d7907d30c719c38cd5a1b (patch)
tree	211439c479f256f76441a8937df956d7fd00d58a
parent	94f744195e17cf787a36c259254d56386b31fe20 (diff)
download	musl-66b53cfa8876342f7e7d7907d30c719c38cd5a1b.tar.gz

ldso: avoid spurious & possible erroneous work for libs with no deps

a null pointer for a library's deps list was ambiguous: it could indicate either no dependencies or that the dependency list had not yet been populated. inability to distinguish could lead to spurious work when dlopen is called multiple times on a library with no deps, and due to related bugs, could actually cause other libraries to falsely appear as dependencies, translating into false positives for dlsym. avoid the problem by always initializing the deps pointer, pointing to an empty list if there are no deps. rather than wasting memory and introducing another failure path by allocating an empty list per library, simply share a global dummy list. further fixes will be needed for related bugs, and much of this code may end up being replaced.

Diffstat

-rw-r--r--

ldso/dynlink.c

1 files changed, 7 insertions, 4 deletions

diff --git a/ldso/dynlink.c b/ldso/dynlink.c
index d20dbd87..239007ff 100644
--- a/ldso/dynlink.c
+++ b/ldso/dynlink.c

@@ -129,6 +129,7 @@ static size_t static_tls_cnt;

static pthread_mutex_t init_fini_lock = { ._m_type = PTHREAD_MUTEX_RECURSIVE };

static struct fdpic_loadmap *app_loadmap;

static struct fdpic_dummy_loadmap app_dummy_loadmap;

+static struct dso *const nodeps_dummy;

struct debug *_dl_debug_addr = &debug;

@@ -1125,6 +1126,7 @@ static void load_deps(struct dso *p)

}

+ if (!*deps) *deps = (struct dso **)&nodeps_dummy;

}

static void load_preload(char *s)

@@ -1742,7 +1744,8 @@ void *dlopen(const char *file, int mode)

free(p->funcdescs);

if (p->rpath != p->rpath_orig)

free(p->rpath);

- free(p->deps);

+ if (p->deps != &nodeps_dummy)

+ free(p->deps);

unmap_library(p);

free(p);

}

@@ -1772,14 +1775,14 @@ void *dlopen(const char *file, int mode)

load_deps(p);

if (!p->relocated && (mode & RTLD_LAZY)) {

prepare_lazy(p);

- if (p->deps) for (i=0; p->deps[i]; i++)

+ for (i=0; p->deps[i]; i++)

if (!p->deps[i]->relocated)

prepare_lazy(p->deps[i]);

}

/* Make new symbols global, at least temporarily, so we can do

* relocations. If not RTLD_GLOBAL, this is reverted below. */

add_syms(p);

- if (p->deps) for (i=0; p->deps[i]; i++)

+ for (i=0; p->deps[i]; i++)

add_syms(p->deps[i]);

reloc_all(p);

}

@@ -1878,7 +1881,7 @@ static void *do_dlsym(struct dso *p, const char *s, void *ra)

return p->funcdescs + (sym - p->syms);

if (sym && sym->st_value && (1<<(sym->st_info&0xf) & OK_TYPES))

return laddr(p, sym->st_value);

- if (p->deps) for (i=0; p->deps[i]; i++) {

+ for (i=0; p->deps[i]; i++) {

if ((ght = p->deps[i]->ghashtab)) {

if (!gh) gh = gnu_hash(s);

sym = gnu_lookup(gh, ght, p->deps[i], s);

generated by cgit v1.2.1 (git 2.18.0) at 2025年10月02日 08:20:21 +0000