[PATCH v4] elf: Also try DT_RUNPATH for LD_AUDIT dlopen [BZ #28455]
H.J. Lu
hjl.tools@gmail.com
Tue Jan 4 00:01:59 GMT 2022
On Mon, Jan 3, 2022 at 12:41 PM Adhemerval Zanella
<adhemerval.zanella@linaro.org> wrote:
>
>
>
> On 15/12/2021 23:06, H.J. Lu via Libc-alpha wrote:
> > Changes in v4:
> >
> > 1. Move the RUNPATH search for LD_AUDIT dlopen after the other RUNPATH
> > search
> > 2. Split one test per line and sort.
> >
> > DT_RUNPATH is only used to find the immediate dependencies of the
> > executable or shared object containing the DT_RUNPATH entry. Update
> > LD_AUDIT dlopen call to try the DT_RUNPATH entry of the executable.
> > This partially fixes BZ #28455.
>
> LGTM, I have only a question below.
>
> > ---
> > elf/Makefile | 20 +++++++++++++++++---
> > elf/dl-load.c | 37 ++++++++++++++++++++++++++++++++-----
> > elf/tst-audit14a.c | 1 +
> > 3 files changed, 50 insertions(+), 8 deletions(-)
> > create mode 100644 elf/tst-audit14a.c
> >
> > diff --git a/elf/Makefile b/elf/Makefile
> > index fe42caeb0e..625b1a023f 100644
> > --- a/elf/Makefile
> > +++ b/elf/Makefile
> > @@ -249,10 +249,19 @@ ifneq ($(selinux-enabled),1)
> > tests-execstack-yes = tst-execstack tst-execstack-needed tst-execstack-prog
> > endif
> > ifeq ($(have-depaudit),yes)
> > -tests += tst-audit14 tst-audit15 tst-audit16
> > +tests += \
> > + tst-audit14 \
> > + tst-audit14a \
> > + tst-audit15 \
> > + tst-audit16 \
> > +
> > ifeq ($(run-built-tests),yes)
> > -tests-special += $(objpfx)tst-audit14-cmp.out $(objpfx)tst-audit15-cmp.out \
> > - $(objpfx)tst-audit16-cmp.out
> > +tests-special += \
> > + $(objpfx)tst-audit14-cmp.out \
> > + $(objpfx)tst-audit14a-cmp.out \
> > + $(objpfx)tst-audit15-cmp.out \
> > + $(objpfx)tst-audit16-cmp.out \
> > +
> > endif
> > endif
> > endif
>
> Ok.
>
> > @@ -1529,6 +1538,8 @@ tst-auditmany-ENV = \
> > LDFLAGS-tst-audit14 = -Wl,--audit=tst-auditlogmod-1.so
> > $(objpfx)tst-auditlogmod-1.so: $(libsupport)
> > $(objpfx)tst-audit14.out: $(objpfx)tst-auditlogmod-1.so
> > +LDFLAGS-tst-audit14a = -Wl,--audit=tst-auditlogmod-1.so,--enable-new-dtags
> > +$(objpfx)tst-audit14a.out: $(objpfx)tst-auditlogmod-1.so
> > LDFLAGS-tst-audit15 = \
> > -Wl,--audit=tst-auditlogmod-1.so,--depaudit=tst-auditlogmod-2.so
> > $(objpfx)tst-auditlogmod-2.so: $(libsupport)
> > @@ -1555,6 +1566,9 @@ tst-audit17-ENV = LD_AUDIT=$(objpfx)tst-auditmod17.so
> > $(objpfx)tst-audit14-cmp.out: tst-audit14.exp $(objpfx)tst-audit14.out
> > cmp $^ > $@; \
> > $(evaluate-test)
> > +$(objpfx)tst-audit14a-cmp.out: tst-audit14.exp $(objpfx)tst-audit14a.out
> > + cmp $^ > $@; \
> > + $(evaluate-test)
> > $(objpfx)tst-audit15-cmp.out: tst-audit15.exp $(objpfx)tst-audit15.out
> > cmp $^ > $@; \
> > $(evaluate-test)
>
> Ok.
>
> > diff --git a/elf/dl-load.c b/elf/dl-load.c
> > index 721593135e..1c90801903 100644
> > --- a/elf/dl-load.c
> > +++ b/elf/dl-load.c
> > @@ -2143,14 +2143,16 @@ _dl_map_object (struct link_map *loader, const char *name,
> >
> > fd = -1;
> >
> > + struct link_map *main_map = GL(dl_ns)[LM_ID_BASE]._ns_loaded;
> > + bool did_main_map;
> > +
> > /* When the object has the RUNPATH information we don't use any
> > RPATHs. */
> > if (loader == NULL || loader->l_info[DT_RUNPATH] == NULL)
> > {
> > /* This is the executable's map (if there is one). Make sure that
> > we do not look at it twice. */
> > - struct link_map *main_map = GL(dl_ns)[LM_ID_BASE]._ns_loaded;
> > - bool did_main_map = false;
> > + did_main_map = false;
> >
> > /* First try the DT_RPATH of the dependent object that caused NAME
> > to be loaded. Then that object's dependent, and on up. */
> > @@ -2186,13 +2188,38 @@ _dl_map_object (struct link_map *loader, const char *name,
> > loader ?: GL(dl_ns)[LM_ID_BASE]._ns_loaded,
> > LA_SER_LIBPATH, &found_other_class);
> >
> > + /* Make sure that we do not look at RUNPATH in the executable
> > + twice. */
> > + did_main_map = false;
> > +
> > /* Look at the RUNPATH information for this binary. */
> > if (fd == -1 && loader != NULL
> > && cache_rpath (loader, &loader->l_runpath_dirs,
> > DT_RUNPATH, "RUNPATH"))
> > - fd = open_path (name, namelen, mode,
> > - &loader->l_runpath_dirs, &realname, &fb, loader,
> > - LA_SER_RUNPATH, &found_other_class);
> > + {
> > + did_main_map = loader == main_map;
> > + fd = open_path (name, namelen, mode,
> > + &loader->l_runpath_dirs, &realname, &fb, loader,
> > + LA_SER_RUNPATH, &found_other_class);
> > + }
> > +
> > + /* When processing the lookup we may need to additionally try
> > + DT_RUNPATH in the executable for a glibc internal dlopen call
> > + when looking for audit modules. */
> > + if (__glibc_unlikely (mode & __RTLD_AUDIT)
> > + && fd == -1
> > + && !did_main_map
> > + && main_map != NULL
>
> When main_map would be NULL? For namespaces different than LM_ID_BASE it
> does make sense, but I think it is assumed in a lot of places that
> for LM_ID_BASE that _ns_loaded is always non-NULL (even for static
> linking dl-support guarantees it).
I simplified it in the v5 patch. But I kept the main_map check since it is
also checked for DT_RPATH in the executable.
> > + && main_map->l_type != lt_loaded)
> > + {
> > + struct r_search_path_struct l_rpath_dirs;
> > + l_rpath_dirs.dirs = NULL;
> > + if (cache_rpath (main_map, &l_rpath_dirs,
> > + DT_RUNPATH, "RUNPATH"))
> > + fd = open_path (name, namelen, mode, &l_rpath_dirs,
> > + &realname, &fb, loader ?: main_map,
> > + LA_SER_RUNPATH, &found_other_class);
> > + }
> >
> > if (fd == -1)
> > {
> > diff --git a/elf/tst-audit14a.c b/elf/tst-audit14a.c
> > new file mode 100644
> > index 0000000000..c6232eacf2
> > --- /dev/null
> > +++ b/elf/tst-audit14a.c
> > @@ -0,0 +1 @@
> > +#include "tst-audit14.c"
>
> Add a comment that it checks the -Wl,--enable-new-dtags. Should we also
> enforce --disable-new-dtags for tst-audit14 ?
Fixed in the v5:
https://patchwork.sourceware.org/project/glibc/patch/20220103235753.2062518-2-hjl.tools@gmail.com/
Thanks.
--
H.J.
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