* [PATCH v12 0/2] arm64: Enable BTI for the executable as well as the interpreter @ 2022-04-04 9:44 ` Mark Brown 0 siblings, 0 replies; 6+ messages in thread From: Mark Brown @ 2022-04-04 9:44 UTC (permalink / raw) To: Catalin Marinas, Will Deacon Cc: Szabolcs Nagy, Jeremy Linton, H . J . Lu, Yu-cheng Yu, Kees Cook, Eric Biederman, linux-arch, linux-arm-kernel, libc-alpha, Mark Brown Deployments of BTI on arm64 have run into issues interacting with systemd's MemoryDenyWriteExecute feature. Currently for dynamically linked executables the kernel will only handle architecture specific properties like BTI for the interpreter, the expectation is that the interpreter will then handle any properties on the main executable. For BTI this means remapping the executable segments PROT_EXEC | PROT_BTI. This interacts poorly with MemoryDenyWriteExecute since that is implemented using a seccomp filter which prevents setting PROT_EXEC on already mapped memory and lacks the context to be able to detect that memory is already mapped with PROT_EXEC. This series resolves this by providing a sysctl which when enabled will cause the kernel to handle the BTI property for both the interpreter and the main executable. v12: - Rebase onto v5.18-rc1. v11: - Ignore extra PT_INTERPs. v10: - Add a sysctl abi.bti_main controlling the new behaviour. v9: - Rebase onto v5.17-rc3. v8: - Rebase onto v5.17-rc1. v7: - Rebase onto v5.16-rc1. v6: - Rebase onto v5.15-rc1. v5: - Rebase onto v5.14-rc2. - Tweak changelog on patch 1. - Use the helper for interpreter/executable flag in elf.h as well. v4: - Rebase onto v5.14-rc1. v3: - Fix passing of properties for parsing by the main executable. - Drop has_interp from arch_parse_elf_property(). - Coding style tweaks. v2: - Add a patch dropping has_interp from arch_adjust_elf_prot() - Fix bisection issue with static executables on arm64 in the first patch. Mark Brown (2): elf: Allow architectures to parse properties on the main executable arm64: Enable BTI for main executable as well as the interpreter arch/arm64/include/asm/elf.h | 14 ++++++++-- arch/arm64/kernel/process.c | 52 +++++++++++++++++++++++++++--------- fs/binfmt_elf.c | 34 ++++++++++++++++------- include/linux/elf.h | 4 ++- 4 files changed, 78 insertions(+), 26 deletions(-) base-commit: 3123109284176b1532874591f7c81f3837bbdc17 -- 2.30.2 ^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH v12 0/2] arm64: Enable BTI for the executable as well as the interpreter @ 2022-04-04 9:44 ` Mark Brown 0 siblings, 0 replies; 6+ messages in thread From: Mark Brown @ 2022-04-04 9:44 UTC (permalink / raw) To: Catalin Marinas, Will Deacon Cc: Szabolcs Nagy, Jeremy Linton, H . J . Lu, Yu-cheng Yu, Kees Cook, Eric Biederman, linux-arch, linux-arm-kernel, libc-alpha, Mark Brown Deployments of BTI on arm64 have run into issues interacting with systemd's MemoryDenyWriteExecute feature. Currently for dynamically linked executables the kernel will only handle architecture specific properties like BTI for the interpreter, the expectation is that the interpreter will then handle any properties on the main executable. For BTI this means remapping the executable segments PROT_EXEC | PROT_BTI. This interacts poorly with MemoryDenyWriteExecute since that is implemented using a seccomp filter which prevents setting PROT_EXEC on already mapped memory and lacks the context to be able to detect that memory is already mapped with PROT_EXEC. This series resolves this by providing a sysctl which when enabled will cause the kernel to handle the BTI property for both the interpreter and the main executable. v12: - Rebase onto v5.18-rc1. v11: - Ignore extra PT_INTERPs. v10: - Add a sysctl abi.bti_main controlling the new behaviour. v9: - Rebase onto v5.17-rc3. v8: - Rebase onto v5.17-rc1. v7: - Rebase onto v5.16-rc1. v6: - Rebase onto v5.15-rc1. v5: - Rebase onto v5.14-rc2. - Tweak changelog on patch 1. - Use the helper for interpreter/executable flag in elf.h as well. v4: - Rebase onto v5.14-rc1. v3: - Fix passing of properties for parsing by the main executable. - Drop has_interp from arch_parse_elf_property(). - Coding style tweaks. v2: - Add a patch dropping has_interp from arch_adjust_elf_prot() - Fix bisection issue with static executables on arm64 in the first patch. Mark Brown (2): elf: Allow architectures to parse properties on the main executable arm64: Enable BTI for main executable as well as the interpreter arch/arm64/include/asm/elf.h | 14 ++++++++-- arch/arm64/kernel/process.c | 52 +++++++++++++++++++++++++++--------- fs/binfmt_elf.c | 34 ++++++++++++++++------- include/linux/elf.h | 4 ++- 4 files changed, 78 insertions(+), 26 deletions(-) base-commit: 3123109284176b1532874591f7c81f3837bbdc17 -- 2.30.2 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel ^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH v12 1/2] elf: Allow architectures to parse properties on the main executable 2022-04-04 9:44 ` Mark Brown @ 2022-04-04 9:44 ` Mark Brown -1 siblings, 0 replies; 6+ messages in thread From: Mark Brown @ 2022-04-04 9:44 UTC (permalink / raw) To: Catalin Marinas, Will Deacon Cc: Szabolcs Nagy, Jeremy Linton, H . J . Lu, Yu-cheng Yu, Kees Cook, Eric Biederman, linux-arch, linux-arm-kernel, libc-alpha, Mark Brown, Dave Martin Currently the ELF code only attempts to parse properties on the image that will start execution, either the interpreter or for statically linked executables the main executable. The expectation is that any property handling for the main executable will be done by the interpreter. This is a bit inconsistent since we do map the executable and is causing problems for the arm64 BTI support when used in conjunction with systemd's use of seccomp to implement MemoryDenyWriteExecute which stops the dynamic linker adjusting the permissions of executable segments. Allow architectures to handle properties for both the dynamic linker and main executable, adjusting arch_parse_elf_properties() to have a new flag is_interp flag as with arch_elf_adjust_prot() and calling it for both the main executable and any intepreter. The user of this code, arm64, is adapted to ensure that there is no functional change. Signed-off-by: Mark Brown <broonie@kernel.org> Tested-by: Jeremy Linton <jeremy.linton@arm.com> Reviewed-by: Dave Martin <Dave.Martin@arm.com> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> --- arch/arm64/include/asm/elf.h | 3 ++- fs/binfmt_elf.c | 34 ++++++++++++++++++++++++---------- include/linux/elf.h | 4 +++- 3 files changed, 29 insertions(+), 12 deletions(-) diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h index 97932fbf973d..5cc002376abe 100644 --- a/arch/arm64/include/asm/elf.h +++ b/arch/arm64/include/asm/elf.h @@ -259,6 +259,7 @@ struct arch_elf_state { static inline int arch_parse_elf_property(u32 type, const void *data, size_t datasz, bool compat, + bool has_interp, bool is_interp, struct arch_elf_state *arch) { /* No known properties for AArch32 yet */ @@ -271,7 +272,7 @@ static inline int arch_parse_elf_property(u32 type, const void *data, if (datasz != sizeof(*p)) return -ENOEXEC; - if (system_supports_bti() && + if (system_supports_bti() && has_interp == is_interp && (*p & GNU_PROPERTY_AARCH64_FEATURE_1_BTI)) arch->flags |= ARM64_ELF_BTI; } diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index 6556e13ed95f..ecd462bddb7e 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -717,8 +717,9 @@ static unsigned long load_elf_interp(struct elfhdr *interp_elf_ex, */ static int parse_elf_property(const char *data, size_t *off, size_t datasz, - struct arch_elf_state *arch, - bool have_prev_type, u32 *prev_type) + struct arch_elf_state *arch, bool has_interp, + bool is_interp, bool have_prev_type, + u32 *prev_type) { size_t o, step; const struct gnu_property *pr; @@ -752,7 +753,8 @@ static int parse_elf_property(const char *data, size_t *off, size_t datasz, *prev_type = pr->pr_type; ret = arch_parse_elf_property(pr->pr_type, data + o, - pr->pr_datasz, ELF_COMPAT, arch); + pr->pr_datasz, ELF_COMPAT, + has_interp, is_interp, arch); if (ret) return ret; @@ -765,6 +767,7 @@ static int parse_elf_property(const char *data, size_t *off, size_t datasz, #define NOTE_NAME_SZ (sizeof(GNU_PROPERTY_TYPE_0_NAME)) static int parse_elf_properties(struct file *f, const struct elf_phdr *phdr, + bool has_interp, bool is_interp, struct arch_elf_state *arch) { union { @@ -814,7 +817,8 @@ static int parse_elf_properties(struct file *f, const struct elf_phdr *phdr, have_prev_type = false; do { ret = parse_elf_property(note.data, &off, datasz, arch, - have_prev_type, &prev_type); + has_interp, is_interp, have_prev_type, + &prev_type); have_prev_type = true; } while (!ret); @@ -829,6 +833,7 @@ static int load_elf_binary(struct linux_binprm *bprm) unsigned long error; struct elf_phdr *elf_ppnt, *elf_phdata, *interp_elf_phdata = NULL; struct elf_phdr *elf_property_phdata = NULL; + struct elf_phdr *interp_elf_property_phdata = NULL; unsigned long elf_bss, elf_brk; int bss_prot = 0; int retval, i; @@ -866,12 +871,15 @@ static int load_elf_binary(struct linux_binprm *bprm) for (i = 0; i < elf_ex->e_phnum; i++, elf_ppnt++) { char *elf_interpreter; + if (interpreter && elf_property_phdata) + break; + if (elf_ppnt->p_type == PT_GNU_PROPERTY) { elf_property_phdata = elf_ppnt; continue; } - if (elf_ppnt->p_type != PT_INTERP) + if (interpreter || elf_ppnt->p_type != PT_INTERP) continue; /* @@ -920,7 +928,7 @@ static int load_elf_binary(struct linux_binprm *bprm) if (retval < 0) goto out_free_dentry; - break; + continue; out_free_interp: kfree(elf_interpreter); @@ -964,12 +972,11 @@ static int load_elf_binary(struct linux_binprm *bprm) goto out_free_dentry; /* Pass PT_LOPROC..PT_HIPROC headers to arch code */ - elf_property_phdata = NULL; elf_ppnt = interp_elf_phdata; for (i = 0; i < interp_elf_ex->e_phnum; i++, elf_ppnt++) switch (elf_ppnt->p_type) { case PT_GNU_PROPERTY: - elf_property_phdata = elf_ppnt; + interp_elf_property_phdata = elf_ppnt; break; case PT_LOPROC ... PT_HIPROC: @@ -980,10 +987,17 @@ static int load_elf_binary(struct linux_binprm *bprm) goto out_free_dentry; break; } + + retval = parse_elf_properties(interpreter, + interp_elf_property_phdata, + true, true, &arch_state); + if (retval) + goto out_free_dentry; + } - retval = parse_elf_properties(interpreter ?: bprm->file, - elf_property_phdata, &arch_state); + retval = parse_elf_properties(bprm->file, elf_property_phdata, + interpreter, false, &arch_state); if (retval) goto out_free_dentry; diff --git a/include/linux/elf.h b/include/linux/elf.h index c9a46c4e183b..1c45ecf29147 100644 --- a/include/linux/elf.h +++ b/include/linux/elf.h @@ -88,13 +88,15 @@ struct arch_elf_state; #ifndef CONFIG_ARCH_USE_GNU_PROPERTY static inline int arch_parse_elf_property(u32 type, const void *data, size_t datasz, bool compat, + bool has_interp, bool is_interp, struct arch_elf_state *arch) { return 0; } #else extern int arch_parse_elf_property(u32 type, const void *data, size_t datasz, - bool compat, struct arch_elf_state *arch); + bool compat, bool has_interp, bool is_interp, + struct arch_elf_state *arch); #endif #ifdef CONFIG_ARCH_HAVE_ELF_PROT -- 2.30.2 ^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH v12 1/2] elf: Allow architectures to parse properties on the main executable @ 2022-04-04 9:44 ` Mark Brown 0 siblings, 0 replies; 6+ messages in thread From: Mark Brown @ 2022-04-04 9:44 UTC (permalink / raw) To: Catalin Marinas, Will Deacon Cc: Szabolcs Nagy, Jeremy Linton, H . J . Lu, Yu-cheng Yu, Kees Cook, Eric Biederman, linux-arch, linux-arm-kernel, libc-alpha, Mark Brown, Dave Martin Currently the ELF code only attempts to parse properties on the image that will start execution, either the interpreter or for statically linked executables the main executable. The expectation is that any property handling for the main executable will be done by the interpreter. This is a bit inconsistent since we do map the executable and is causing problems for the arm64 BTI support when used in conjunction with systemd's use of seccomp to implement MemoryDenyWriteExecute which stops the dynamic linker adjusting the permissions of executable segments. Allow architectures to handle properties for both the dynamic linker and main executable, adjusting arch_parse_elf_properties() to have a new flag is_interp flag as with arch_elf_adjust_prot() and calling it for both the main executable and any intepreter. The user of this code, arm64, is adapted to ensure that there is no functional change. Signed-off-by: Mark Brown <broonie@kernel.org> Tested-by: Jeremy Linton <jeremy.linton@arm.com> Reviewed-by: Dave Martin <Dave.Martin@arm.com> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> --- arch/arm64/include/asm/elf.h | 3 ++- fs/binfmt_elf.c | 34 ++++++++++++++++++++++++---------- include/linux/elf.h | 4 +++- 3 files changed, 29 insertions(+), 12 deletions(-) diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h index 97932fbf973d..5cc002376abe 100644 --- a/arch/arm64/include/asm/elf.h +++ b/arch/arm64/include/asm/elf.h @@ -259,6 +259,7 @@ struct arch_elf_state { static inline int arch_parse_elf_property(u32 type, const void *data, size_t datasz, bool compat, + bool has_interp, bool is_interp, struct arch_elf_state *arch) { /* No known properties for AArch32 yet */ @@ -271,7 +272,7 @@ static inline int arch_parse_elf_property(u32 type, const void *data, if (datasz != sizeof(*p)) return -ENOEXEC; - if (system_supports_bti() && + if (system_supports_bti() && has_interp == is_interp && (*p & GNU_PROPERTY_AARCH64_FEATURE_1_BTI)) arch->flags |= ARM64_ELF_BTI; } diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index 6556e13ed95f..ecd462bddb7e 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -717,8 +717,9 @@ static unsigned long load_elf_interp(struct elfhdr *interp_elf_ex, */ static int parse_elf_property(const char *data, size_t *off, size_t datasz, - struct arch_elf_state *arch, - bool have_prev_type, u32 *prev_type) + struct arch_elf_state *arch, bool has_interp, + bool is_interp, bool have_prev_type, + u32 *prev_type) { size_t o, step; const struct gnu_property *pr; @@ -752,7 +753,8 @@ static int parse_elf_property(const char *data, size_t *off, size_t datasz, *prev_type = pr->pr_type; ret = arch_parse_elf_property(pr->pr_type, data + o, - pr->pr_datasz, ELF_COMPAT, arch); + pr->pr_datasz, ELF_COMPAT, + has_interp, is_interp, arch); if (ret) return ret; @@ -765,6 +767,7 @@ static int parse_elf_property(const char *data, size_t *off, size_t datasz, #define NOTE_NAME_SZ (sizeof(GNU_PROPERTY_TYPE_0_NAME)) static int parse_elf_properties(struct file *f, const struct elf_phdr *phdr, + bool has_interp, bool is_interp, struct arch_elf_state *arch) { union { @@ -814,7 +817,8 @@ static int parse_elf_properties(struct file *f, const struct elf_phdr *phdr, have_prev_type = false; do { ret = parse_elf_property(note.data, &off, datasz, arch, - have_prev_type, &prev_type); + has_interp, is_interp, have_prev_type, + &prev_type); have_prev_type = true; } while (!ret); @@ -829,6 +833,7 @@ static int load_elf_binary(struct linux_binprm *bprm) unsigned long error; struct elf_phdr *elf_ppnt, *elf_phdata, *interp_elf_phdata = NULL; struct elf_phdr *elf_property_phdata = NULL; + struct elf_phdr *interp_elf_property_phdata = NULL; unsigned long elf_bss, elf_brk; int bss_prot = 0; int retval, i; @@ -866,12 +871,15 @@ static int load_elf_binary(struct linux_binprm *bprm) for (i = 0; i < elf_ex->e_phnum; i++, elf_ppnt++) { char *elf_interpreter; + if (interpreter && elf_property_phdata) + break; + if (elf_ppnt->p_type == PT_GNU_PROPERTY) { elf_property_phdata = elf_ppnt; continue; } - if (elf_ppnt->p_type != PT_INTERP) + if (interpreter || elf_ppnt->p_type != PT_INTERP) continue; /* @@ -920,7 +928,7 @@ static int load_elf_binary(struct linux_binprm *bprm) if (retval < 0) goto out_free_dentry; - break; + continue; out_free_interp: kfree(elf_interpreter); @@ -964,12 +972,11 @@ static int load_elf_binary(struct linux_binprm *bprm) goto out_free_dentry; /* Pass PT_LOPROC..PT_HIPROC headers to arch code */ - elf_property_phdata = NULL; elf_ppnt = interp_elf_phdata; for (i = 0; i < interp_elf_ex->e_phnum; i++, elf_ppnt++) switch (elf_ppnt->p_type) { case PT_GNU_PROPERTY: - elf_property_phdata = elf_ppnt; + interp_elf_property_phdata = elf_ppnt; break; case PT_LOPROC ... PT_HIPROC: @@ -980,10 +987,17 @@ static int load_elf_binary(struct linux_binprm *bprm) goto out_free_dentry; break; } + + retval = parse_elf_properties(interpreter, + interp_elf_property_phdata, + true, true, &arch_state); + if (retval) + goto out_free_dentry; + } - retval = parse_elf_properties(interpreter ?: bprm->file, - elf_property_phdata, &arch_state); + retval = parse_elf_properties(bprm->file, elf_property_phdata, + interpreter, false, &arch_state); if (retval) goto out_free_dentry; diff --git a/include/linux/elf.h b/include/linux/elf.h index c9a46c4e183b..1c45ecf29147 100644 --- a/include/linux/elf.h +++ b/include/linux/elf.h @@ -88,13 +88,15 @@ struct arch_elf_state; #ifndef CONFIG_ARCH_USE_GNU_PROPERTY static inline int arch_parse_elf_property(u32 type, const void *data, size_t datasz, bool compat, + bool has_interp, bool is_interp, struct arch_elf_state *arch) { return 0; } #else extern int arch_parse_elf_property(u32 type, const void *data, size_t datasz, - bool compat, struct arch_elf_state *arch); + bool compat, bool has_interp, bool is_interp, + struct arch_elf_state *arch); #endif #ifdef CONFIG_ARCH_HAVE_ELF_PROT -- 2.30.2 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel ^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH v12 2/2] arm64: Enable BTI for main executable as well as the interpreter 2022-04-04 9:44 ` Mark Brown @ 2022-04-04 9:44 ` Mark Brown -1 siblings, 0 replies; 6+ messages in thread From: Mark Brown @ 2022-04-04 9:44 UTC (permalink / raw) To: Catalin Marinas, Will Deacon Cc: Szabolcs Nagy, Jeremy Linton, H . J . Lu, Yu-cheng Yu, Kees Cook, Eric Biederman, linux-arch, linux-arm-kernel, libc-alpha, Mark Brown Currently for dynamically linked ELF executables we only enable BTI for the interpreter, expecting the interpreter to do this for the main executable. This is a bit inconsistent since we do map main executable and is causing issues with systemd's MemoryDenyWriteExecute feature which is implemented using a seccomp filter which prevents setting PROT_EXEC on already mapped memory and lacks the context to be able to detect that memory is already mapped with PROT_EXEC. Resolve this by adding a sysctl abi.bti_main which causes the kernel to checking the BTI property for the main executable and enable BTI if it is present when doing the initial mapping. This sysctl is disabled by default. Signed-off-by: Mark Brown <broonie@kernel.org> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> --- arch/arm64/include/asm/elf.h | 15 ++++++++--- arch/arm64/kernel/process.c | 52 +++++++++++++++++++++++++++--------- 2 files changed, 51 insertions(+), 16 deletions(-) diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h index 5cc002376abe..c4aa60db76a4 100644 --- a/arch/arm64/include/asm/elf.h +++ b/arch/arm64/include/asm/elf.h @@ -251,12 +251,21 @@ struct arch_elf_state { int flags; }; -#define ARM64_ELF_BTI (1 << 0) +#define ARM64_ELF_INTERP_BTI (1 << 0) +#define ARM64_ELF_EXEC_BTI (1 << 1) #define INIT_ARCH_ELF_STATE { \ .flags = 0, \ } +static inline int arm64_elf_bti_flag(bool is_interp) +{ + if (is_interp) + return ARM64_ELF_INTERP_BTI; + else + return ARM64_ELF_EXEC_BTI; +} + static inline int arch_parse_elf_property(u32 type, const void *data, size_t datasz, bool compat, bool has_interp, bool is_interp, @@ -272,9 +281,9 @@ static inline int arch_parse_elf_property(u32 type, const void *data, if (datasz != sizeof(*p)) return -ENOEXEC; - if (system_supports_bti() && has_interp == is_interp && + if (system_supports_bti() && (*p & GNU_PROPERTY_AARCH64_FEATURE_1_BTI)) - arch->flags |= ARM64_ELF_BTI; + arch->flags |= arm64_elf_bti_flag(is_interp); } return 0; diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index 7fa97df55e3a..665d375cc3f1 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -702,23 +702,49 @@ core_initcall(tagged_addr_init); #endif /* CONFIG_ARM64_TAGGED_ADDR_ABI */ #ifdef CONFIG_BINFMT_ELF +static unsigned int bti_main; + int arch_elf_adjust_prot(int prot, const struct arch_elf_state *state, bool has_interp, bool is_interp) { - /* - * For dynamically linked executables the interpreter is - * responsible for setting PROT_BTI on everything except - * itself. - */ - if (is_interp != has_interp) - return prot; - - if (!(state->flags & ARM64_ELF_BTI)) - return prot; - - if (prot & PROT_EXEC) + if ((prot & PROT_EXEC) && + (is_interp || !has_interp || bti_main) && + (state->flags & arm64_elf_bti_flag(is_interp))) prot |= PROT_BTI; return prot; } -#endif + +#ifdef CONFIG_ARM64_BTI +/* + * If this sysctl is enabled then we will apply PROT_BTI to the main + * executable as well as the dynamic linker if it has the appropriate + * ELF note. It is disabled by default, in which case we will only + * apply PROT_BTI to the dynamic linker or static binaries. + */ +static struct ctl_table bti_main_sysctl_table[] = { + { + .procname = "bti_main", + .mode = 0644, + .data = &bti_main, + .maxlen = sizeof(int), + .proc_handler = proc_dointvec_minmax, + .extra1 = SYSCTL_ZERO, + .extra2 = SYSCTL_ONE, + }, + { } +}; + +static int __init bti_main_init(void) +{ + if (!system_supports_bti()) + return 0; + + if (!register_sysctl("abi", bti_main_sysctl_table)) + return -EINVAL; + return 0; +} +core_initcall(bti_main_init); +#endif /* CONFIG_ARM64_BTI */ + +#endif /* CONFIG_BINFMT_ELF */ -- 2.30.2 ^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH v12 2/2] arm64: Enable BTI for main executable as well as the interpreter @ 2022-04-04 9:44 ` Mark Brown 0 siblings, 0 replies; 6+ messages in thread From: Mark Brown @ 2022-04-04 9:44 UTC (permalink / raw) To: Catalin Marinas, Will Deacon Cc: Szabolcs Nagy, Jeremy Linton, H . J . Lu, Yu-cheng Yu, Kees Cook, Eric Biederman, linux-arch, linux-arm-kernel, libc-alpha, Mark Brown Currently for dynamically linked ELF executables we only enable BTI for the interpreter, expecting the interpreter to do this for the main executable. This is a bit inconsistent since we do map main executable and is causing issues with systemd's MemoryDenyWriteExecute feature which is implemented using a seccomp filter which prevents setting PROT_EXEC on already mapped memory and lacks the context to be able to detect that memory is already mapped with PROT_EXEC. Resolve this by adding a sysctl abi.bti_main which causes the kernel to checking the BTI property for the main executable and enable BTI if it is present when doing the initial mapping. This sysctl is disabled by default. Signed-off-by: Mark Brown <broonie@kernel.org> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> --- arch/arm64/include/asm/elf.h | 15 ++++++++--- arch/arm64/kernel/process.c | 52 +++++++++++++++++++++++++++--------- 2 files changed, 51 insertions(+), 16 deletions(-) diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h index 5cc002376abe..c4aa60db76a4 100644 --- a/arch/arm64/include/asm/elf.h +++ b/arch/arm64/include/asm/elf.h @@ -251,12 +251,21 @@ struct arch_elf_state { int flags; }; -#define ARM64_ELF_BTI (1 << 0) +#define ARM64_ELF_INTERP_BTI (1 << 0) +#define ARM64_ELF_EXEC_BTI (1 << 1) #define INIT_ARCH_ELF_STATE { \ .flags = 0, \ } +static inline int arm64_elf_bti_flag(bool is_interp) +{ + if (is_interp) + return ARM64_ELF_INTERP_BTI; + else + return ARM64_ELF_EXEC_BTI; +} + static inline int arch_parse_elf_property(u32 type, const void *data, size_t datasz, bool compat, bool has_interp, bool is_interp, @@ -272,9 +281,9 @@ static inline int arch_parse_elf_property(u32 type, const void *data, if (datasz != sizeof(*p)) return -ENOEXEC; - if (system_supports_bti() && has_interp == is_interp && + if (system_supports_bti() && (*p & GNU_PROPERTY_AARCH64_FEATURE_1_BTI)) - arch->flags |= ARM64_ELF_BTI; + arch->flags |= arm64_elf_bti_flag(is_interp); } return 0; diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index 7fa97df55e3a..665d375cc3f1 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -702,23 +702,49 @@ core_initcall(tagged_addr_init); #endif /* CONFIG_ARM64_TAGGED_ADDR_ABI */ #ifdef CONFIG_BINFMT_ELF +static unsigned int bti_main; + int arch_elf_adjust_prot(int prot, const struct arch_elf_state *state, bool has_interp, bool is_interp) { - /* - * For dynamically linked executables the interpreter is - * responsible for setting PROT_BTI on everything except - * itself. - */ - if (is_interp != has_interp) - return prot; - - if (!(state->flags & ARM64_ELF_BTI)) - return prot; - - if (prot & PROT_EXEC) + if ((prot & PROT_EXEC) && + (is_interp || !has_interp || bti_main) && + (state->flags & arm64_elf_bti_flag(is_interp))) prot |= PROT_BTI; return prot; } -#endif + +#ifdef CONFIG_ARM64_BTI +/* + * If this sysctl is enabled then we will apply PROT_BTI to the main + * executable as well as the dynamic linker if it has the appropriate + * ELF note. It is disabled by default, in which case we will only + * apply PROT_BTI to the dynamic linker or static binaries. + */ +static struct ctl_table bti_main_sysctl_table[] = { + { + .procname = "bti_main", + .mode = 0644, + .data = &bti_main, + .maxlen = sizeof(int), + .proc_handler = proc_dointvec_minmax, + .extra1 = SYSCTL_ZERO, + .extra2 = SYSCTL_ONE, + }, + { } +}; + +static int __init bti_main_init(void) +{ + if (!system_supports_bti()) + return 0; + + if (!register_sysctl("abi", bti_main_sysctl_table)) + return -EINVAL; + return 0; +} +core_initcall(bti_main_init); +#endif /* CONFIG_ARM64_BTI */ + +#endif /* CONFIG_BINFMT_ELF */ -- 2.30.2 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel ^ permalink raw reply related [flat|nested] 6+ messages in thread
end of thread, other threads:[~2022-04-04 9:45 UTC | newest] Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2022-04-04 9:44 [PATCH v12 0/2] arm64: Enable BTI for the executable as well as the interpreter Mark Brown 2022-04-04 9:44 ` Mark Brown 2022-04-04 9:44 ` [PATCH v12 1/2] elf: Allow architectures to parse properties on the main executable Mark Brown 2022-04-04 9:44 ` Mark Brown 2022-04-04 9:44 ` [PATCH v12 2/2] arm64: Enable BTI for main executable as well as the interpreter Mark Brown 2022-04-04 9:44 ` Mark Brown
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