diff mbox series

x32: Handle displacement overflow in PLT rewrite [BZ #31218]

Message ID 20240106220337.1665359-1-hjl.tools@gmail.com
State New
Headers show
Series x32: Handle displacement overflow in PLT rewrite [BZ #31218] | expand

Commit Message

H.J. Lu Jan. 6, 2024, 10:03 p.m. UTC
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

Noah Goldstein Jan. 6, 2024, 10:23 p.m. UTC | #1
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>
diff mbox series

Patch

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);
+}