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Groups > linux.kernel > #1630128
| From | Kees Cook <keescook@chromium.org> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH v7 1/4] syscalls: Restore address limit after a syscall |
| Date | 2017-04-25 02:00 +0200 |
| Message-ID | <tzW3E-5co-13@gated-at.bofh.it> (permalink) |
| References | <tuL8T-3IQ-35@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Mon, Apr 10, 2017 at 9:44 AM, Thomas Garnier <thgarnie@google.com> wrote:
> This patch ensures a syscall does not return to user-mode with a kernel
> address limit. If that happened, a process can corrupt kernel-mode
> memory and elevate privileges.
>
> For example, it would mitigation this bug:
>
> - https://bugs.chromium.org/p/project-zero/issues/detail?id=990
>
> The CONFIG_ARCH_NO_SYSCALL_VERIFY_PRE_USERMODE_STATE option is also
> added so each architecture can optimize this change.
>
> Signed-off-by: Thomas Garnier <thgarnie@google.com>
> Tested-by: Kees Cook <keescook@chromium.org>
Ingo, I think this series is ready. Can you pull it? (And if not, what
should next steps be?)
-Kees
> ---
> Based on next-20170410
> ---
> arch/s390/Kconfig | 1 +
> include/linux/syscalls.h | 26 +++++++++++++++++++++++++-
> init/Kconfig | 6 ++++++
> kernel/sys.c | 13 +++++++++++++
> 4 files changed, 45 insertions(+), 1 deletion(-)
>
> diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
> index d25435d94b6e..489a0cc6e46b 100644
> --- a/arch/s390/Kconfig
> +++ b/arch/s390/Kconfig
> @@ -103,6 +103,7 @@ config S390
> select ARCH_INLINE_WRITE_UNLOCK_BH
> select ARCH_INLINE_WRITE_UNLOCK_IRQ
> select ARCH_INLINE_WRITE_UNLOCK_IRQRESTORE
> + select ARCH_NO_SYSCALL_VERIFY_PRE_USERMODE_STATE
> select ARCH_SAVE_PAGE_KEYS if HIBERNATION
> select ARCH_SUPPORTS_ATOMIC_RMW
> select ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT
> diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
> index 980c3c9b06f8..801a7a74fe28 100644
> --- a/include/linux/syscalls.h
> +++ b/include/linux/syscalls.h
> @@ -191,6 +191,27 @@ extern struct trace_event_functions exit_syscall_print_funcs;
> SYSCALL_METADATA(sname, x, __VA_ARGS__) \
> __SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
>
> +
> +/*
> + * Called before coming back to user-mode. Returning to user-mode with an
> + * address limit different than USER_DS can allow to overwrite kernel memory.
> + */
> +static inline void verify_pre_usermode_state(void) {
> + BUG_ON(!segment_eq(get_fs(), USER_DS));
> +}
> +
> +#ifndef CONFIG_ARCH_NO_SYSCALL_VERIFY_PRE_USERMODE_STATE
> +#define __CHECK_USER_CALLER() \
> + bool user_caller = segment_eq(get_fs(), USER_DS)
> +#define __VERIFY_PRE_USERMODE_STATE() \
> + if (user_caller) verify_pre_usermode_state()
> +#else
> +#define __CHECK_USER_CALLER()
> +#define __VERIFY_PRE_USERMODE_STATE()
> +asmlinkage void address_limit_check_failed(void);
> +#endif
> +
> +
> #define __PROTECT(...) asmlinkage_protect(__VA_ARGS__)
> #define __SYSCALL_DEFINEx(x, name, ...) \
> asmlinkage long sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)) \
> @@ -199,7 +220,10 @@ extern struct trace_event_functions exit_syscall_print_funcs;
> asmlinkage long SyS##name(__MAP(x,__SC_LONG,__VA_ARGS__)); \
> asmlinkage long SyS##name(__MAP(x,__SC_LONG,__VA_ARGS__)) \
> { \
> - long ret = SYSC##name(__MAP(x,__SC_CAST,__VA_ARGS__)); \
> + long ret; \
> + __CHECK_USER_CALLER(); \
> + ret = SYSC##name(__MAP(x,__SC_CAST,__VA_ARGS__)); \
> + __VERIFY_PRE_USERMODE_STATE(); \
> __MAP(x,__SC_TEST,__VA_ARGS__); \
> __PROTECT(x, ret,__MAP(x,__SC_ARGS,__VA_ARGS__)); \
> return ret; \
> diff --git a/init/Kconfig b/init/Kconfig
> index 7f7027817bce..e5fbd0becfa7 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -1958,6 +1958,12 @@ config PROFILING
> config TRACEPOINTS
> bool
>
> +config ARCH_NO_SYSCALL_VERIFY_PRE_USERMODE_STATE
> + bool
> + help
> + Disable the generic pre-usermode state verification. Allow each
> + architecture to optimize how and when the verification is done.
> +
> source "arch/Kconfig"
>
> endmenu # General setup
> diff --git a/kernel/sys.c b/kernel/sys.c
> index 196c7134bee6..d30530ff8166 100644
> --- a/kernel/sys.c
> +++ b/kernel/sys.c
> @@ -2459,3 +2459,16 @@ COMPAT_SYSCALL_DEFINE1(sysinfo, struct compat_sysinfo __user *, info)
> return 0;
> }
> #endif /* CONFIG_COMPAT */
> +
> +#ifdef CONFIG_ARCH_NO_SYSCALL_VERIFY_PRE_USERMODE_STATE
> +/*
> + * This function is called when an architecture specific implementation detected
> + * an invalid address limit. The generic user-mode state checker will finish on
> + * the appropriate BUG_ON.
> + */
> +asmlinkage void address_limit_check_failed(void)
> +{
> + verify_pre_usermode_state();
> + panic("address_limit_check_failed called with a valid user-mode state");
> +}
> +#endif
> --
> 2.12.2.715.g7642488e1d-goog
>
--
Kees Cook
Pixel Security
Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
[PATCH v7 1/4] syscalls: Restore address limit after a syscall Thomas Garnier <thgarnie@google.com> - 2017-04-10 20:00 +0200
[PATCH v7 3/4] arm/syscalls: Architecture specific pre-usermode check Thomas Garnier <thgarnie@google.com> - 2017-04-10 20:00 +0200
[PATCH v7 2/4] x86/syscalls: Architecture specific pre-usermode check Thomas Garnier <thgarnie@google.com> - 2017-04-10 20:00 +0200
[PATCH v7 4/4] arm64/syscalls: Architecture specific pre-usermode check Thomas Garnier <thgarnie@google.com> - 2017-04-10 20:00 +0200
Re: [PATCH v7 1/4] syscalls: Restore address limit after a syscall Kees Cook <keescook@chromium.org> - 2017-04-25 02:00 +0200
Re: [PATCH v7 1/4] syscalls: Restore address limit after a syscall Ingo Molnar <mingo@kernel.org> - 2017-04-25 08:30 +0200
Re: [PATCH v7 1/4] syscalls: Restore address limit after a syscall Thomas Garnier <thgarnie@google.com> - 2017-04-25 16:20 +0200
Re: [PATCH v7 1/4] syscalls: Restore address limit after a syscall Ingo Molnar <mingo@kernel.org> - 2017-04-25 08:40 +0200
Re: [PATCH v7 1/4] syscalls: Restore address limit after a syscall Thomas Garnier <thgarnie@google.com> - 2017-04-25 16:20 +0200
Re: [PATCH v7 1/4] syscalls: Restore address limit after a syscall Ingo Molnar <mingo@kernel.org> - 2017-04-26 10:20 +0200
Re: [PATCH v7 1/4] syscalls: Restore address limit after a syscall Thomas Garnier <thgarnie@google.com> - 2017-04-26 16:10 +0200
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