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