| Message ID | 20230302224946.never.243-kees@kernel.org (mailing list archive) |
|---|---|
| State | Mainlined |
| Commit | b69edab47f1da8edd8e7bfdf8c70f51a2a5d89fb |
| Headers | show |
| Series | kheaders: Use array declaration instead of char | expand |
On Thu, Mar 02, 2023 at 02:49:50PM -0800, Kees Cook wrote: > Under CONFIG_FORTIFY_SOURCE, memcpy() will check the size of destination > and source buffers. Defining kernel_headers_data as "char" would trip > this check. Since these addresses are treated as byte arrays, define > them as arrays (as done everywhere else). > > This was seen with: > > $ cat /sys/kernel/kheaders.tar.xz >> /dev/null > > detected buffer overflow in memcpy > kernel BUG at lib/string_helpers.c:1027! > ... > RIP: 0010:fortify_panic+0xf/0x20 > [...] > Call Trace: > <TASK> > ikheaders_read+0x45/0x50 [kheaders] > kernfs_fop_read_iter+0x1a4/0x2f0 > ... > > Reported-by: Jakub Kicinski <kuba@kernel.org> > Link: https://lore.kernel.org/bpf/20230302112130.6e402a98@kernel.org/ > Tested-by: Jakub Kicinski <kuba@kernel.org> Acked-by: Joel Fernandes (Google) <joel@joelfernandes.org> thanks, - Joel > Fixes: 43d8ce9d65a5 ("Provide in-kernel headers to make extending kernel easier") > Cc: Joel Fernandes (Google) <joel@joelfernandes.org> > Cc: stable@vger.kernel.org > Signed-off-by: Kees Cook <keescook@chromium.org> > --- > kernel/kheaders.c | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/kernel/kheaders.c b/kernel/kheaders.c > index 8f69772af77b..42163c9e94e5 100644 > --- a/kernel/kheaders.c > +++ b/kernel/kheaders.c > @@ -26,15 +26,15 @@ asm ( > " .popsection \n" > ); > > -extern char kernel_headers_data; > -extern char kernel_headers_data_end; > +extern char kernel_headers_data[]; > +extern char kernel_headers_data_end[]; > > static ssize_t > ikheaders_read(struct file *file, struct kobject *kobj, > struct bin_attribute *bin_attr, > char *buf, loff_t off, size_t len) > { > - memcpy(buf, &kernel_headers_data + off, len); > + memcpy(buf, &kernel_headers_data[off], len); > return len; > } > > @@ -48,8 +48,8 @@ static struct bin_attribute kheaders_attr __ro_after_init = { > > static int __init ikheaders_init(void) > { > - kheaders_attr.size = (&kernel_headers_data_end - > - &kernel_headers_data); > + kheaders_attr.size = (kernel_headers_data_end - > + kernel_headers_data); > return sysfs_create_bin_file(kernel_kobj, &kheaders_attr); > } > > -- > 2.34.1 >
From: Kees Cook <keescook@chromium.org> Date: Thu, 2 Mar 2023 14:49:50 -0800 > Under CONFIG_FORTIFY_SOURCE, memcpy() will check the size of destination > and source buffers. Defining kernel_headers_data as "char" would trip > this check. Since these addresses are treated as byte arrays, define > them as arrays (as done everywhere else). Yet another array-as-one-char, I wonder how many are still here... > > This was seen with: > > $ cat /sys/kernel/kheaders.tar.xz >> /dev/null > > detected buffer overflow in memcpy > kernel BUG at lib/string_helpers.c:1027! > ... > RIP: 0010:fortify_panic+0xf/0x20 > [...] > Call Trace: > <TASK> > ikheaders_read+0x45/0x50 [kheaders] > kernfs_fop_read_iter+0x1a4/0x2f0 > ... > > Reported-by: Jakub Kicinski <kuba@kernel.org> > Link: https://lore.kernel.org/bpf/20230302112130.6e402a98@kernel.org/ > Tested-by: Jakub Kicinski <kuba@kernel.org> > Fixes: 43d8ce9d65a5 ("Provide in-kernel headers to make extending kernel easier") > Cc: Joel Fernandes (Google) <joel@joelfernandes.org> > Cc: stable@vger.kernel.org > Signed-off-by: Kees Cook <keescook@chromium.org> Reviewed-by: Alexander Lobakin <aleksander.lobakin@intel.com> > --- > kernel/kheaders.c | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) [...] Thanks, Olek
On Fri, Mar 03, 2023 at 04:19:51PM +0100, Alexander Lobakin wrote: > From: Kees Cook <keescook@chromium.org> > Date: Thu, 2 Mar 2023 14:49:50 -0800 > > > Under CONFIG_FORTIFY_SOURCE, memcpy() will check the size of destination > > and source buffers. Defining kernel_headers_data as "char" would trip > > this check. Since these addresses are treated as byte arrays, define > > them as arrays (as done everywhere else). > > Yet another array-as-one-char, I wonder how many are still here... Yeah, good point. They do tend to stand out; we could find them: $ git grep 'extern char [^\*\[\( ]*;' arch/alpha/boot/bootp.c:extern char _end; arch/alpha/boot/bootpz.c:extern char _end; arch/alpha/boot/main.c: extern char _end; arch/arm/mach-rockchip/core.h:extern char rockchip_secondary_trampoline; arch/arm/mach-rockchip/core.h:extern char rockchip_secondary_trampoline_end; arch/arm/mach-zynq/common.h:extern char zynq_secondary_trampoline; arch/arm/mach-zynq/common.h:extern char zynq_secondary_trampoline_jump; arch/arm/mach-zynq/common.h:extern char zynq_secondary_trampoline_end; arch/hexagon/include/uapi/asm/setup.h:extern char external_cmdline_buffer; arch/ia64/include/asm/smp.h:extern char no_int_routing; arch/ia64/kernel/process.c: extern char ia64_ret_from_clone; arch/mips/dec/prom/memory.c: extern char genexcept_early; arch/mips/kernel/traps.c: extern char except_vec3_generic; arch/mips/kernel/traps.c: extern char except_vec4; arch/mips/kernel/traps.c: extern char except_vec3_r4000; arch/mips/mm/c-octeon.c: extern char except_vec2_octeon; arch/parisc/boot/compressed/misc.c:extern char output_len; arch/parisc/boot/compressed/misc.c:extern char _startcode_end; arch/powerpc/include/asm/smp.h:extern char __secondary_hold; arch/s390/include/asm/kvm_host.h:extern char sie_exit; arch/sh/boards/mach-ap325rxa/setup.c:extern char ap325rxa_sdram_enter_start; arch/sh/boards/mach-ap325rxa/setup.c:extern char ap325rxa_sdram_enter_end; arch/sh/boards/mach-ap325rxa/setup.c:extern char ap325rxa_sdram_leave_start; arch/sh/boards/mach-ap325rxa/setup.c:extern char ap325rxa_sdram_leave_end; arch/sh/boards/mach-ecovec24/setup.c:extern char ecovec24_sdram_enter_start; arch/sh/boards/mach-ecovec24/setup.c:extern char ecovec24_sdram_enter_end; arch/sh/boards/mach-ecovec24/setup.c:extern char ecovec24_sdram_leave_start; arch/sh/boards/mach-ecovec24/setup.c:extern char ecovec24_sdram_leave_end; arch/sh/boards/mach-kfr2r09/setup.c:extern char kfr2r09_sdram_enter_start; arch/sh/boards/mach-kfr2r09/setup.c:extern char kfr2r09_sdram_enter_end; arch/sh/boards/mach-kfr2r09/setup.c:extern char kfr2r09_sdram_leave_start; arch/sh/boards/mach-kfr2r09/setup.c:extern char kfr2r09_sdram_leave_end; arch/sh/boards/mach-migor/setup.c:extern char migor_sdram_enter_start; arch/sh/boards/mach-migor/setup.c:extern char migor_sdram_enter_end; arch/sh/boards/mach-migor/setup.c:extern char migor_sdram_leave_start; arch/sh/boards/mach-migor/setup.c:extern char migor_sdram_leave_end; arch/sh/boards/mach-se/7724/setup.c:extern char ms7724se_sdram_enter_start; arch/sh/boards/mach-se/7724/setup.c:extern char ms7724se_sdram_enter_end; arch/sh/boards/mach-se/7724/setup.c:extern char ms7724se_sdram_leave_start; arch/sh/boards/mach-se/7724/setup.c:extern char ms7724se_sdram_leave_end; arch/sh/kernel/cpu/shmobile/pm.c:extern char sh_mobile_sleep_enter_start; arch/sh/kernel/cpu/shmobile/pm.c:extern char sh_mobile_sleep_enter_end; arch/sh/kernel/cpu/shmobile/pm.c:extern char sh_mobile_sleep_resume_start; arch/sh/kernel/cpu/shmobile/pm.c:extern char sh_mobile_sleep_resume_end; arch/x86/entry/vsyscall/vsyscall_64.c: extern char __vsyscall_page; arch/x86/include/asm/vvar.h:extern char __vvar_page; kernel/configs.c:extern char kernel_config_data; kernel/configs.c:extern char kernel_config_data_end; net/bpfilter/bpfilter_kern.c:extern char bpfilter_umh_start; net/bpfilter/bpfilter_kern.c:extern char bpfilter_umh_end; samples/bpf/task_fd_query_user.c: extern char __executable_start; tools/testing/selftests/kvm/lib/aarch64/processor.c: extern char vectors; tools/testing/selftests/x86/test_syscall_vdso.c:extern char int80; Of those, it looks like only a handful might trip FORTIFY: $ for i in $(git grep 'extern char [^\*\[\( ]*;' | grep -v boot/ | awk -F' ' '{print $NF}' | cut -d';' -f1); do git grep -E '(strcpy|memcpy|memset).*'"$i",; done arch/arm/mach-rockchip/platsmp.c: memcpy_toio(sram_base_addr, &rockchip_secondary_trampoline, trampoline_sz); arch/arm/mach-zynq/platsmp.c: memcpy_toio(zero, &zynq_secondary_trampoline, arch/mips/dec/prom/memory.c: memcpy((void *)(CKSEG0 + 0x80), &genexcept_early, 0x80); arch/sh/kernel/cpu/shmobile/pm.c: memcpy(vp, &sh_mobile_sleep_enter_start, n); arch/sh/kernel/cpu/shmobile/pm.c: memcpy(vp, &sh_mobile_sleep_resume_start, n); arch/arm64/mm/trans_pgd.c: memcpy(hyp_stub, &trans_pgd_stub_vectors, ARM64_VECTOR_TABLE_LEN);
From: Kees Cook <keescook@chromium.org> Date: Fri, 3 Mar 2023 12:36:09 -0800 > On Fri, Mar 03, 2023 at 04:19:51PM +0100, Alexander Lobakin wrote: >> From: Kees Cook <keescook@chromium.org> >> Date: Thu, 2 Mar 2023 14:49:50 -0800 >> >>> Under CONFIG_FORTIFY_SOURCE, memcpy() will check the size of destination >>> and source buffers. Defining kernel_headers_data as "char" would trip >>> this check. Since these addresses are treated as byte arrays, define >>> them as arrays (as done everywhere else). >> >> Yet another array-as-one-char, I wonder how many are still here... > > Yeah, good point. They do tend to stand out; we could find them: > > $ git grep 'extern char [^\*\[\( ]*;' > arch/alpha/boot/bootp.c:extern char _end; > arch/alpha/boot/bootpz.c:extern char _end; > arch/alpha/boot/main.c: extern char _end; > arch/arm/mach-rockchip/core.h:extern char rockchip_secondary_trampoline; > arch/arm/mach-rockchip/core.h:extern char rockchip_secondary_trampoline_end; > arch/arm/mach-zynq/common.h:extern char zynq_secondary_trampoline; > arch/arm/mach-zynq/common.h:extern char zynq_secondary_trampoline_jump; > arch/arm/mach-zynq/common.h:extern char zynq_secondary_trampoline_end; > arch/hexagon/include/uapi/asm/setup.h:extern char external_cmdline_buffer; > arch/ia64/include/asm/smp.h:extern char no_int_routing; > arch/ia64/kernel/process.c: extern char ia64_ret_from_clone; > arch/mips/dec/prom/memory.c: extern char genexcept_early; > arch/mips/kernel/traps.c: extern char except_vec3_generic; > arch/mips/kernel/traps.c: extern char except_vec4; > arch/mips/kernel/traps.c: extern char except_vec3_r4000; > arch/mips/mm/c-octeon.c: extern char except_vec2_octeon; > arch/parisc/boot/compressed/misc.c:extern char output_len; > arch/parisc/boot/compressed/misc.c:extern char _startcode_end; > arch/powerpc/include/asm/smp.h:extern char __secondary_hold; > arch/s390/include/asm/kvm_host.h:extern char sie_exit; > arch/sh/boards/mach-ap325rxa/setup.c:extern char ap325rxa_sdram_enter_start; > arch/sh/boards/mach-ap325rxa/setup.c:extern char ap325rxa_sdram_enter_end; > arch/sh/boards/mach-ap325rxa/setup.c:extern char ap325rxa_sdram_leave_start; > arch/sh/boards/mach-ap325rxa/setup.c:extern char ap325rxa_sdram_leave_end; > arch/sh/boards/mach-ecovec24/setup.c:extern char ecovec24_sdram_enter_start; > arch/sh/boards/mach-ecovec24/setup.c:extern char ecovec24_sdram_enter_end; > arch/sh/boards/mach-ecovec24/setup.c:extern char ecovec24_sdram_leave_start; > arch/sh/boards/mach-ecovec24/setup.c:extern char ecovec24_sdram_leave_end; > arch/sh/boards/mach-kfr2r09/setup.c:extern char kfr2r09_sdram_enter_start; > arch/sh/boards/mach-kfr2r09/setup.c:extern char kfr2r09_sdram_enter_end; > arch/sh/boards/mach-kfr2r09/setup.c:extern char kfr2r09_sdram_leave_start; > arch/sh/boards/mach-kfr2r09/setup.c:extern char kfr2r09_sdram_leave_end; > arch/sh/boards/mach-migor/setup.c:extern char migor_sdram_enter_start; > arch/sh/boards/mach-migor/setup.c:extern char migor_sdram_enter_end; > arch/sh/boards/mach-migor/setup.c:extern char migor_sdram_leave_start; > arch/sh/boards/mach-migor/setup.c:extern char migor_sdram_leave_end; > arch/sh/boards/mach-se/7724/setup.c:extern char ms7724se_sdram_enter_start; > arch/sh/boards/mach-se/7724/setup.c:extern char ms7724se_sdram_enter_end; > arch/sh/boards/mach-se/7724/setup.c:extern char ms7724se_sdram_leave_start; > arch/sh/boards/mach-se/7724/setup.c:extern char ms7724se_sdram_leave_end; > arch/sh/kernel/cpu/shmobile/pm.c:extern char sh_mobile_sleep_enter_start; > arch/sh/kernel/cpu/shmobile/pm.c:extern char sh_mobile_sleep_enter_end; > arch/sh/kernel/cpu/shmobile/pm.c:extern char sh_mobile_sleep_resume_start; > arch/sh/kernel/cpu/shmobile/pm.c:extern char sh_mobile_sleep_resume_end; > arch/x86/entry/vsyscall/vsyscall_64.c: extern char __vsyscall_page; > arch/x86/include/asm/vvar.h:extern char __vvar_page; > kernel/configs.c:extern char kernel_config_data; > kernel/configs.c:extern char kernel_config_data_end; > net/bpfilter/bpfilter_kern.c:extern char bpfilter_umh_start; > net/bpfilter/bpfilter_kern.c:extern char bpfilter_umh_end; > samples/bpf/task_fd_query_user.c: extern char __executable_start; > tools/testing/selftests/kvm/lib/aarch64/processor.c: extern char vectors; > tools/testing/selftests/x86/test_syscall_vdso.c:extern char int80; > > Of those, it looks like only a handful might trip FORTIFY: > > $ for i in $(git grep 'extern char [^\*\[\( ]*;' | grep -v boot/ | awk -F' ' '{print $NF}' | cut -d';' -f1); do git grep -E '(strcpy|memcpy|memset).*'"$i",; done > arch/arm/mach-rockchip/platsmp.c: memcpy_toio(sram_base_addr, &rockchip_secondary_trampoline, trampoline_sz); > arch/arm/mach-zynq/platsmp.c: memcpy_toio(zero, &zynq_secondary_trampoline, > arch/mips/dec/prom/memory.c: memcpy((void *)(CKSEG0 + 0x80), &genexcept_early, 0x80); > arch/sh/kernel/cpu/shmobile/pm.c: memcpy(vp, &sh_mobile_sleep_enter_start, n); > arch/sh/kernel/cpu/shmobile/pm.c: memcpy(vp, &sh_mobile_sleep_resume_start, n); > arch/arm64/mm/trans_pgd.c: memcpy(hyp_stub, &trans_pgd_stub_vectors, ARM64_VECTOR_TABLE_LEN); > > This list looks much better than the first one :D I remember I caught a couple fortify bugs due to such array declaration on MIPS only when testing with `KCFLAGS=-O3`. The thing was that a pointer to such array-not-array was passed as a function argument and that function wasn't inlined on -O2. So I sometimes use this optlevel for sanity-checking the code :P Thanks, Olek
diff --git a/kernel/kheaders.c b/kernel/kheaders.c index 8f69772af77b..42163c9e94e5 100644 --- a/kernel/kheaders.c +++ b/kernel/kheaders.c @@ -26,15 +26,15 @@ asm ( " .popsection \n" ); -extern char kernel_headers_data; -extern char kernel_headers_data_end; +extern char kernel_headers_data[]; +extern char kernel_headers_data_end[]; static ssize_t ikheaders_read(struct file *file, struct kobject *kobj, struct bin_attribute *bin_attr, char *buf, loff_t off, size_t len) { - memcpy(buf, &kernel_headers_data + off, len); + memcpy(buf, &kernel_headers_data[off], len); return len; } @@ -48,8 +48,8 @@ static struct bin_attribute kheaders_attr __ro_after_init = { static int __init ikheaders_init(void) { - kheaders_attr.size = (&kernel_headers_data_end - - &kernel_headers_data); + kheaders_attr.size = (kernel_headers_data_end - + kernel_headers_data); return sysfs_create_bin_file(kernel_kobj, &kheaders_attr); }