x32: Handle displacement overflow in PLT rewrite [BZ #31218]
Checks
| Context |
Check |
Description |
| redhat-pt-bot/TryBot-apply_patch |
success
|
Patch applied to master at the time it was sent
|
| linaro-tcwg-bot/tcwg_glibc_build--master-aarch64 |
fail
|
Patch failed to apply
|
| redhat-pt-bot/TryBot-32bit |
success
|
Build for i686
|
| linaro-tcwg-bot/tcwg_glibc_build--master-arm |
success
|
Testing passed
|
| linaro-tcwg-bot/tcwg_glibc_check--master-arm |
fail
|
Patch failed to apply
|
Commit Message
PLT rewrite calculated displacement with
ElfW(Addr) disp = value - branch_start - JMP32_INSN_SIZE;
On x32, displacement from 0xf7fbe060 to 0x401030 was calculated as
unsigned int disp = 0x401030 - 0xf7fbe060 - 5;
with disp == 0x8442fcb and caused displacement overflow. The PLT entry
was changed to:
0xf7fbe060 <+0>: e9 cb 2f 44 08 jmp 0x401030
0xf7fbe065 <+5>: cc int3
0xf7fbe066 <+6>: cc int3
0xf7fbe067 <+7>: cc int3
0xf7fbe068 <+8>: cc int3
0xf7fbe069 <+9>: cc int3
0xf7fbe06a <+10>: cc int3
0xf7fbe06b <+11>: cc int3
0xf7fbe06c <+12>: cc int3
0xf7fbe06d <+13>: cc int3
0xf7fbe06e <+14>: cc int3
0xf7fbe06f <+15>: cc int3
x32 has 32-bit address range, but it doesn't wrap address around at 4GB,
JMP target was changed to 0x100401030 (0xf7fbe060LL + 0x8442fcbLL + 5),
which is above 4GB.
Always use uint64_t to calculate displacement. This fixes BZ #31218.
---
sysdeps/x86_64/Makefile | 8 +++++
sysdeps/x86_64/dl-machine.h | 5 +--
sysdeps/x86_64/tst-plt-rewrite2.c | 46 ++++++++++++++++++++++++++++
sysdeps/x86_64/tst-plt-rewritemod2.c | 32 +++++++++++++++++++
4 files changed, 89 insertions(+), 2 deletions(-)
create mode 100644 sysdeps/x86_64/tst-plt-rewrite2.c
create mode 100644 sysdeps/x86_64/tst-plt-rewritemod2.c
Comments
On Sat, Jan 6, 2024 at 2:03 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> PLT rewrite calculated displacement with
>
> ElfW(Addr) disp = value - branch_start - JMP32_INSN_SIZE;
>
> On x32, displacement from 0xf7fbe060 to 0x401030 was calculated as
>
> unsigned int disp = 0x401030 - 0xf7fbe060 - 5;
>
> with disp == 0x8442fcb and caused displacement overflow. The PLT entry
> was changed to:
>
> 0xf7fbe060 <+0>: e9 cb 2f 44 08 jmp 0x401030
> 0xf7fbe065 <+5>: cc int3
> 0xf7fbe066 <+6>: cc int3
> 0xf7fbe067 <+7>: cc int3
> 0xf7fbe068 <+8>: cc int3
> 0xf7fbe069 <+9>: cc int3
> 0xf7fbe06a <+10>: cc int3
> 0xf7fbe06b <+11>: cc int3
> 0xf7fbe06c <+12>: cc int3
> 0xf7fbe06d <+13>: cc int3
> 0xf7fbe06e <+14>: cc int3
> 0xf7fbe06f <+15>: cc int3
>
> x32 has 32-bit address range, but it doesn't wrap address around at 4GB,
> JMP target was changed to 0x100401030 (0xf7fbe060LL + 0x8442fcbLL + 5),
> which is above 4GB.
>
> Always use uint64_t to calculate displacement. This fixes BZ #31218.
> ---
> sysdeps/x86_64/Makefile | 8 +++++
> sysdeps/x86_64/dl-machine.h | 5 +--
> sysdeps/x86_64/tst-plt-rewrite2.c | 46 ++++++++++++++++++++++++++++
> sysdeps/x86_64/tst-plt-rewritemod2.c | 32 +++++++++++++++++++
> 4 files changed, 89 insertions(+), 2 deletions(-)
> create mode 100644 sysdeps/x86_64/tst-plt-rewrite2.c
> create mode 100644 sysdeps/x86_64/tst-plt-rewritemod2.c
>
> diff --git a/sysdeps/x86_64/Makefile b/sysdeps/x86_64/Makefile
> index 374bca80d0..836e03a224 100644
> --- a/sysdeps/x86_64/Makefile
> +++ b/sysdeps/x86_64/Makefile
> @@ -186,9 +186,11 @@ endif
> ifeq (yes,$(have-z-mark-plt))
> tests += \
> tst-plt-rewrite1 \
> + tst-plt-rewrite2 \
> # tests
> modules-names += \
> tst-plt-rewritemod1 \
> + tst-plt-rewritemod2 \
> # modules-names
>
> tst-plt-rewrite1-no-pie = yes
> @@ -200,6 +202,12 @@ $(objpfx)tst-plt-rewrite1.out: /dev/null $(objpfx)tst-plt-rewrite1
> $(tst-plt-rewrite1-ENV) $(make-test-out) > $@ 2>&1; \
> grep -q -E "changing 'bar' PLT entry in .*/elf/tst-plt-rewritemod1.so' to direct branch" $@; \
> $(evaluate-test)
> +
> +tst-plt-rewrite2-no-pie = yes
> +LDFLAGS-tst-plt-rewrite2 = -Wl,-z,now
> +LDFLAGS-tst-plt-rewritemod2.so = -Wl,-z,now,-z,undefs
> +tst-plt-rewrite2-ENV = GLIBC_TUNABLES=glibc.cpu.plt_rewrite=2
> +$(objpfx)tst-plt-rewrite2: $(objpfx)tst-plt-rewritemod2.so
> endif
>
> endif # $(subdir) == elf
> diff --git a/sysdeps/x86_64/dl-machine.h b/sysdeps/x86_64/dl-machine.h
> index ca290ef082..2d2ce503a5 100644
> --- a/sysdeps/x86_64/dl-machine.h
> +++ b/sysdeps/x86_64/dl-machine.h
> @@ -607,8 +607,9 @@ x86_64_rewrite_plt (struct link_map *map, ElfW(Addr) plt_rewrite)
> /* Skip ENDBR64 if IBT isn't enabled. */
> if (!ibt_enabled_p)
> branch_start = ALIGN_DOWN (branch_start, pltent);
> - /* Get the displacement from the branch target. */
> - ElfW(Addr) disp = value - branch_start - JMP32_INSN_SIZE;
> + /* Get the displacement from the branch target. NB: We must use
> + 64-bit integer on x32 to avoid overflow. */
> + uint64_t disp = (uint64_t) value - branch_start - JMP32_INSN_SIZE;
> ElfW(Addr) plt_end;
> ElfW(Addr) pad;
>
> diff --git a/sysdeps/x86_64/tst-plt-rewrite2.c b/sysdeps/x86_64/tst-plt-rewrite2.c
> new file mode 100644
> index 0000000000..8427df5605
> --- /dev/null
> +++ b/sysdeps/x86_64/tst-plt-rewrite2.c
> @@ -0,0 +1,46 @@
> +/* Test PLT rewrite with 32-bit displacement overflow.
> + Copyright (C) 2024 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/>. */
> +
> +#include <support/check.h>
> +
> +extern int (*func_p) (void);
> +extern void foo (void);
> +
> +int
> +func (void)
> +{
> + return 0xbadbeef;
> +}
> +
> +void
> +bar (void)
> +{
> + TEST_VERIFY (func_p == &func);
> + TEST_VERIFY (func_p () == 0xbadbeef);
> +}
> +
> +static int
> +do_test (void)
> +{
> + func_p = &func;
> + foo ();
> + bar ();
> + return 0;
> +}
> +
> +#include <support/test-driver.c>
> diff --git a/sysdeps/x86_64/tst-plt-rewritemod2.c b/sysdeps/x86_64/tst-plt-rewritemod2.c
> new file mode 100644
> index 0000000000..4a86d736b5
> --- /dev/null
> +++ b/sysdeps/x86_64/tst-plt-rewritemod2.c
> @@ -0,0 +1,32 @@
> +/* Check PLT rewrite with 32-bit displacement overflow.
> + Copyright (C) 2024 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/>. */
> +
> +/* foo calls func with indirect branch via PLT. PLT rewrite shouldn't
> + change it to direct branch if func is too far way. */
> +
> +#include <support/check.h>
> +
> +int (*func_p) (void);
> +extern int func (void);
> +
> +void
> +foo (void)
> +{
> + TEST_VERIFY (func () == 0xbadbeef);
> + TEST_VERIFY (func_p () == 0xbadbeef);
> +}
> --
> 2.43.0
>
LGTM.
Reviewed-by: Noah Goldstein <goldstein.w.n@gmail.com>
@@ -186,9 +186,11 @@ endif
ifeq (yes,$(have-z-mark-plt))
tests += \
tst-plt-rewrite1 \
+ tst-plt-rewrite2 \
# tests
modules-names += \
tst-plt-rewritemod1 \
+ tst-plt-rewritemod2 \
# modules-names
tst-plt-rewrite1-no-pie = yes
@@ -200,6 +202,12 @@ $(objpfx)tst-plt-rewrite1.out: /dev/null $(objpfx)tst-plt-rewrite1
$(tst-plt-rewrite1-ENV) $(make-test-out) > $@ 2>&1; \
grep -q -E "changing 'bar' PLT entry in .*/elf/tst-plt-rewritemod1.so' to direct branch" $@; \
$(evaluate-test)
+
+tst-plt-rewrite2-no-pie = yes
+LDFLAGS-tst-plt-rewrite2 = -Wl,-z,now
+LDFLAGS-tst-plt-rewritemod2.so = -Wl,-z,now,-z,undefs
+tst-plt-rewrite2-ENV = GLIBC_TUNABLES=glibc.cpu.plt_rewrite=2
+$(objpfx)tst-plt-rewrite2: $(objpfx)tst-plt-rewritemod2.so
endif
endif # $(subdir) == elf
@@ -607,8 +607,9 @@ x86_64_rewrite_plt (struct link_map *map, ElfW(Addr) plt_rewrite)
/* Skip ENDBR64 if IBT isn't enabled. */
if (!ibt_enabled_p)
branch_start = ALIGN_DOWN (branch_start, pltent);
- /* Get the displacement from the branch target. */
- ElfW(Addr) disp = value - branch_start - JMP32_INSN_SIZE;
+ /* Get the displacement from the branch target. NB: We must use
+ 64-bit integer on x32 to avoid overflow. */
+ uint64_t disp = (uint64_t) value - branch_start - JMP32_INSN_SIZE;
ElfW(Addr) plt_end;
ElfW(Addr) pad;
new file mode 100644
@@ -0,0 +1,46 @@
+/* Test PLT rewrite with 32-bit displacement overflow.
+ Copyright (C) 2024 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/>. */
+
+#include <support/check.h>
+
+extern int (*func_p) (void);
+extern void foo (void);
+
+int
+func (void)
+{
+ return 0xbadbeef;
+}
+
+void
+bar (void)
+{
+ TEST_VERIFY (func_p == &func);
+ TEST_VERIFY (func_p () == 0xbadbeef);
+}
+
+static int
+do_test (void)
+{
+ func_p = &func;
+ foo ();
+ bar ();
+ return 0;
+}
+
+#include <support/test-driver.c>
new file mode 100644
@@ -0,0 +1,32 @@
+/* Check PLT rewrite with 32-bit displacement overflow.
+ Copyright (C) 2024 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/>. */
+
+/* foo calls func with indirect branch via PLT. PLT rewrite shouldn't
+ change it to direct branch if func is too far way. */
+
+#include <support/check.h>
+
+int (*func_p) (void);
+extern int func (void);
+
+void
+foo (void)
+{
+ TEST_VERIFY (func () == 0xbadbeef);
+ TEST_VERIFY (func_p () == 0xbadbeef);
+}