* [PATCH v2] elf: Stop with zero entry point value [BZ #28453]
@ 2021-12-10 2:40 H.J. Lu
2021-12-10 4:26 ` Siddhesh Poyarekar
0 siblings, 1 reply; 2+ messages in thread
From: H.J. Lu @ 2021-12-10 2:40 UTC (permalink / raw)
To: libc-alpha
Changes in the v2 patch:
1. Use rtld_progname in the error message.
Stop with zero entry point value unless we are tracing shared objects
since a zero entry point value in the ELF header indicates there is no
associated entry point. Now we get
$ ./elf/ld.so /lib64/libstdc++.so.6.0.29
./elf/ld.so: cannot execute '/lib64/libstdc++.so.6.0.29' without entry point
$
instead of
$ /lib64/ld-linux-x86-64.so.2 /lib64/libstdc++.so.6.0.29
Segmentation fault (core dumped)
$
This fixes [BZ #28453].
---
elf/Makefile | 10 ++++++++++
elf/rtld.c | 8 ++++++++
elf/tst-rtld-run-dso.sh | 33 +++++++++++++++++++++++++++++++++
3 files changed, 51 insertions(+)
create mode 100755 elf/tst-rtld-run-dso.sh
diff --git a/elf/Makefile b/elf/Makefile
index ef36008673..1832dfa537 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -50,6 +50,10 @@ ifeq (yesyes,$(build-shared)$(run-built-tests))
tests-special += $(objpfx)list-tunables.out
endif
+ifeq (yes,$(build-shared))
+tests-special += $(objpfx)tst-rtld-run-dso.out
+endif
+
# Make sure that the compiler does not insert any library calls in tunables
# code paths.
ifeq (yes,$(have-loop-to-function))
@@ -1877,6 +1881,12 @@ $(objpfx)list-tunables.out: tst-rtld-list-tunables.sh $(objpfx)ld.so
$(objpfx)/tst-rtld-list-tunables.out > $@; \
$(evaluate-test)
+$(objpfx)tst-rtld-run-dso.out: tst-rtld-run-dso.sh $(objpfx)ld.so \
+ $(objpfx)testobj1.so
+ $(SHELL) tst-rtld-run-dso.sh $(objpfx)ld.so $(objpfx)testobj1.so \
+ '$(test-wrapper-env)' '$(run_program_env)' > $@
+ $(evaluate-test)
+
tst-dst-static-ENV = LD_LIBRARY_PATH='$$ORIGIN'
$(objpfx)tst-rtld-help.out: $(objpfx)ld.so
diff --git a/elf/rtld.c b/elf/rtld.c
index 6ce1e07dc0..b4373ba193 100644
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -1424,6 +1424,14 @@ dl_main (const ElfW(Phdr) *phdr,
implementations which has no real free() function it does not
makes sense to free the old string first. */
main_map->l_name = (char *) "";
+
+ /* Stop if there is no associated entry point and we are not
+ tracing shared objects. */
+ if (main_map->l_entry == main_map->l_addr
+ && state.mode != rtld_mode_trace)
+ _dl_fatal_printf("%s: cannot execute '%s' without entry point\n",
+ ld_so_name, rtld_progname);
+
*user_entry = main_map->l_entry;
/* Set bit indicating this is the main program map. */
diff --git a/elf/tst-rtld-run-dso.sh b/elf/tst-rtld-run-dso.sh
new file mode 100755
index 0000000000..5192f64210
--- /dev/null
+++ b/elf/tst-rtld-run-dso.sh
@@ -0,0 +1,33 @@
+#!/bin/sh
+# Test for ld.so on a shared library with no associated entry point.
+# Copyright (C) 2021 Free Software Foundation, Inc.
+# This file is part of the GNU C Library.
+#
+# The GNU C Library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2.1 of the License, or (at your option) any later version.
+#
+# The GNU C Library is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with the GNU C Library; if not, see
+# <https://www.gnu.org/licenses/>.
+
+set -e
+
+rtld=$1
+dso=$2
+test_wrapper_env=$3
+run_program_env=$4
+
+LC_ALL=C
+export LC_ALL
+
+${test_wrapper_env} \
+${run_program_env} \
+$rtld $dso 2>&1 \
+| grep "cannot execute"
--
2.33.1
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH v2] elf: Stop with zero entry point value [BZ #28453]
2021-12-10 2:40 [PATCH v2] elf: Stop with zero entry point value [BZ #28453] H.J. Lu
@ 2021-12-10 4:26 ` Siddhesh Poyarekar
0 siblings, 0 replies; 2+ messages in thread
From: Siddhesh Poyarekar @ 2021-12-10 4:26 UTC (permalink / raw)
To: H.J. Lu, libc-alpha
On 12/10/21 08:10, H.J. Lu via Libc-alpha wrote:
> Changes in the v2 patch:
>
> 1. Use rtld_progname in the error message.
>
> Stop with zero entry point value unless we are tracing shared objects
> since a zero entry point value in the ELF header indicates there is no
> associated entry point. Now we get
>
> $ ./elf/ld.so /lib64/libstdc++.so.6.0.29
> ./elf/ld.so: cannot execute '/lib64/libstdc++.so.6.0.29' without entry point
> $
>
> instead of
>
> $ /lib64/ld-linux-x86-64.so.2 /lib64/libstdc++.so.6.0.29
> Segmentation fault (core dumped)
> $
>
> This fixes [BZ #28453].
The change that introduced the zero entry point in binutils:
https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=5226a6a892f922ea672e5775c61776830aaf27b7
and original context of the discussion:
https://bugzilla.redhat.com/show_bug.cgi?id=2004952
LGTM.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
> ---
> elf/Makefile | 10 ++++++++++
> elf/rtld.c | 8 ++++++++
> elf/tst-rtld-run-dso.sh | 33 +++++++++++++++++++++++++++++++++
> 3 files changed, 51 insertions(+)
> create mode 100755 elf/tst-rtld-run-dso.sh
>
> diff --git a/elf/Makefile b/elf/Makefile
> index ef36008673..1832dfa537 100644
> --- a/elf/Makefile
> +++ b/elf/Makefile
> @@ -50,6 +50,10 @@ ifeq (yesyes,$(build-shared)$(run-built-tests))
> tests-special += $(objpfx)list-tunables.out
> endif
>
> +ifeq (yes,$(build-shared))
> +tests-special += $(objpfx)tst-rtld-run-dso.out
> +endif
> +
> # Make sure that the compiler does not insert any library calls in tunables
> # code paths.
> ifeq (yes,$(have-loop-to-function))
> @@ -1877,6 +1881,12 @@ $(objpfx)list-tunables.out: tst-rtld-list-tunables.sh $(objpfx)ld.so
> $(objpfx)/tst-rtld-list-tunables.out > $@; \
> $(evaluate-test)
>
> +$(objpfx)tst-rtld-run-dso.out: tst-rtld-run-dso.sh $(objpfx)ld.so \
> + $(objpfx)testobj1.so
> + $(SHELL) tst-rtld-run-dso.sh $(objpfx)ld.so $(objpfx)testobj1.so \
> + '$(test-wrapper-env)' '$(run_program_env)' > $@
> + $(evaluate-test)
> +
> tst-dst-static-ENV = LD_LIBRARY_PATH='$$ORIGIN'
Test. OK.
>
> $(objpfx)tst-rtld-help.out: $(objpfx)ld.so
> diff --git a/elf/rtld.c b/elf/rtld.c
> index 6ce1e07dc0..b4373ba193 100644
> --- a/elf/rtld.c
> +++ b/elf/rtld.c
> @@ -1424,6 +1424,14 @@ dl_main (const ElfW(Phdr) *phdr,
> implementations which has no real free() function it does not
> makes sense to free the old string first. */
> main_map->l_name = (char *) "";
> +
> + /* Stop if there is no associated entry point and we are not
> + tracing shared objects. */
> + if (main_map->l_entry == main_map->l_addr
> + && state.mode != rtld_mode_trace)
> + _dl_fatal_printf("%s: cannot execute '%s' without entry point\n",
> + ld_so_name, rtld_progname);
> +
Bail out if the entry point is same as load address. OK.
> *user_entry = main_map->l_entry;
>
> /* Set bit indicating this is the main program map. */
> diff --git a/elf/tst-rtld-run-dso.sh b/elf/tst-rtld-run-dso.sh
> new file mode 100755
> index 0000000000..5192f64210
> --- /dev/null
> +++ b/elf/tst-rtld-run-dso.sh
> @@ -0,0 +1,33 @@
> +#!/bin/sh
> +# Test for ld.so on a shared library with no associated entry point.
> +# Copyright (C) 2021 Free Software Foundation, Inc.
> +# This file is part of the GNU C Library.
> +#
> +# The GNU C Library is free software; you can redistribute it and/or
> +# modify it under the terms of the GNU Lesser General Public
> +# License as published by the Free Software Foundation; either
> +# version 2.1 of the License, or (at your option) any later version.
> +#
> +# The GNU C Library is distributed in the hope that it will be useful,
> +# but WITHOUT ANY WARRANTY; without even the implied warranty of
> +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> +# Lesser General Public License for more details.
> +#
> +# You should have received a copy of the GNU Lesser General Public
> +# License along with the GNU C Library; if not, see
> +# <https://www.gnu.org/licenses/>.
> +
> +set -e
> +
> +rtld=$1
> +dso=$2
> +test_wrapper_env=$3
> +run_program_env=$4
> +
> +LC_ALL=C
> +export LC_ALL
> +
> +${test_wrapper_env} \
> +${run_program_env} \
> +$rtld $dso 2>&1 \
> +| grep "cannot execute"
>
OK.
Thanks,
Siddhesh
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