From: Will Drewry Date: Thu, 9 Feb 2012 18:08:39 +0000 (-0600) Subject: BACKPORT: ptrace,seccomp: Add PTRACE_SECCOMP support X-Git-Url: http://git.cascardo.eti.br/?a=commitdiff_plain;h=54db11086e4e45afc89f3e36c77f15a8e2bbbb9a;p=cascardo%2Flinux.git BACKPORT: ptrace,seccomp: Add PTRACE_SECCOMP support This change adds support for a new ptrace option, PTRACE_O_TRACESECCOMP, and a new return value for seccomp BPF programs, SECCOMP_RET_TRACE. When a tracer specifies the PTRACE_O_TRACESECCOMP ptrace option, the tracer will be notified, via PTRACE_EVENT_SECCOMP, for any syscall that results in a BPF program returning SECCOMP_RET_TRACE. The 16-bit SECCOMP_RET_DATA mask of the BPF program return value will be passed as the ptrace_message and may be retrieved using PTRACE_GETEVENTMSG. If the subordinate process is not using seccomp filter, then no system call notifications will occur even if the option is specified. If there is no tracer with PTRACE_O_TRACESECCOMP when SECCOMP_RET_TRACE is returned, the system call will not be executed and an -ENOSYS errno will be returned to userspace. This change adds a dependency on the system call slow path. Any future efforts to use the system call fast path for seccomp filter will need to address this restriction. v18: - rebase - comment fatal_signal check - acked-by v17: - ... v16: - update PT_TRACE_MASK to 0xbf4 so that STOP isn't clear on SETOPTIONS call (indan@nul.nu) [note PT_TRACE_MASK disappears in linux-next] v15: - add audit support for non-zero return codes - clean up style (indan@nul.nu) v14: - rebase/nochanges v13: - rebase on to 88ebdda6159ffc15699f204c33feb3e431bf9bdc (Brings back a change to ptrace.c and the masks.) v12: - rebase to linux-next - use ptrace_event and update arch/Kconfig to mention slow-path dependency - drop all tracehook changes and inclusion (oleg@redhat.com) v11: - invert the logic to just make it a PTRACE_SYSCALL accelerator (indan@nul.nu) v10: - moved to PTRACE_O_SECCOMP / PT_TRACE_SECCOMP v9: - n/a v8: - guarded PTRACE_SECCOMP use with an ifdef v7: - introduced Change-Id: I1a6b98cc3dad0be83f856279f850f718a9888b53 Acked-by: Eric Paris Signed-off-by: Will Drewry BUG=chromium-os:27878 TEST=none. Part of a much larger stack that really should merge together. Change-Id: I1ba0786303612deae64878f8a8396541a9553a89 Reviewed-on: https://gerrit.chromium.org/gerrit/21368 Reviewed-by: Will Drewry Tested-by: Will Drewry --- diff --git a/arch/Kconfig b/arch/Kconfig index d5f3869c475f..ed5702dabbde 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -219,15 +219,16 @@ config ARCH_WANT_OLD_COMPAT_IPC config HAVE_ARCH_SECCOMP_FILTER bool help - This symbol should be selected by an architecure if it provides: - asm/syscall.h: + An arch should select this symbol if it provides all of these things: - syscall_get_arch() - syscall_get_arguments() - syscall_rollback() - syscall_set_return_value() - SIGSYS siginfo_t support must be implemented. - __secure_computing_int()/secure_computing()'s return value must be - checked, with -1 resulting in the syscall being skipped. + - SIGSYS siginfo_t support + - uses __secure_computing_int() or secure_computing() + - secure_computing is called from a ptrace_event()-safe context + - secure_computing return value is checked and a return value of -1 + results in the system call being skipped immediately. config SECCOMP_FILTER def_bool y diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h index 5c719627c2aa..26bf736de61b 100644 --- a/include/linux/ptrace.h +++ b/include/linux/ptrace.h @@ -51,6 +51,9 @@ #define PTRACE_INTERRUPT 0x4207 #define PTRACE_LISTEN 0x4208 +/* flags in @data for PTRACE_SEIZE */ +#define PTRACE_SEIZE_DEVEL 0x80000000 /* temp flag for development */ + /* Wait extended result codes for the above trace options. */ #define PTRACE_EVENT_FORK 1 #define PTRACE_EVENT_VFORK 2 @@ -58,6 +61,8 @@ #define PTRACE_EVENT_EXEC 4 #define PTRACE_EVENT_VFORK_DONE 5 #define PTRACE_EVENT_EXIT 6 +#define PTRACE_EVENT_SECCOMP 7 + /* Extended result codes which enabled by means other than options. */ #define PTRACE_EVENT_STOP 128 @@ -69,6 +74,7 @@ #define PTRACE_O_TRACEEXEC (1 << PTRACE_EVENT_EXEC) #define PTRACE_O_TRACEVFORKDONE (1 << PTRACE_EVENT_VFORK_DONE) #define PTRACE_O_TRACEEXIT (1 << PTRACE_EVENT_EXIT) +#define PTRACE_O_TRACESECCOMP (1 << PTRACE_EVENT_SECCOMP) #define PTRACE_O_MASK 0x0000007f @@ -98,6 +104,9 @@ #define PT_TRACE_EXEC PT_EVENT_FLAG(PTRACE_EVENT_EXEC) #define PT_TRACE_VFORK_DONE PT_EVENT_FLAG(PTRACE_EVENT_VFORK_DONE) #define PT_TRACE_EXIT PT_EVENT_FLAG(PTRACE_EVENT_EXIT) +#define PT_TRACE_SECCOMP PT_EVENT_FLAG(PTRACE_EVENT_SECCOMP) + +#define PT_TRACE_MASK 0x000007f4 /* single stepping state bits (used on ARM and PA-RISC) */ #define PT_SINGLESTEP_BIT 31 diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h index ecec06c9bf44..41ff13b7d7ec 100644 --- a/include/linux/seccomp.h +++ b/include/linux/seccomp.h @@ -21,6 +21,7 @@ #define SECCOMP_RET_KILL 0x00000000U /* kill the task immediately */ #define SECCOMP_RET_TRAP 0x00030000U /* disallow and force a SIGSYS */ #define SECCOMP_RET_ERRNO 0x00050000U /* returns an errno */ +#define SECCOMP_RET_TRACE 0x7ff00000U /* pass to a tracer or disallow */ #define SECCOMP_RET_ALLOW 0x7fff0000U /* allow */ /* Masks for the return value sections. */ diff --git a/kernel/ptrace.c b/kernel/ptrace.c index ee8d49b9c309..a51f76bdcd19 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -535,6 +535,9 @@ static int ptrace_setoptions(struct task_struct *child, unsigned long data) flags |= (data << PT_OPT_FLAG_SHIFT); child->ptrace = flags; + if (data & PTRACE_O_TRACESECCOMP) + child->ptrace |= PT_TRACE_SECCOMP; + return 0; } diff --git a/kernel/seccomp.c b/kernel/seccomp.c index b1ec240659ac..aa2faab5ebbe 100644 --- a/kernel/seccomp.c +++ b/kernel/seccomp.c @@ -24,6 +24,7 @@ #ifdef CONFIG_SECCOMP_FILTER #include #include +#include #include #include #include @@ -403,7 +404,7 @@ int __secure_computing_int(int this_syscall) case SECCOMP_MODE_FILTER: ret = seccomp_run_filters(this_syscall); data = ret & SECCOMP_RET_DATA; - switch (code & SECCOMP_RET_ACTION) { + switch (ret & SECCOMP_RET_ACTION) { case SECCOMP_RET_ERRNO: /* Set the low-order 16-bits as a errno. */ syscall_set_return_value(current, task_pt_regs(current), @@ -415,6 +416,21 @@ int __secure_computing_int(int this_syscall) /* Let the filter pass back 16 bits of data. */ seccomp_send_sigsys(this_syscall, data); goto skip; + case SECCOMP_RET_TRACE: + /* Skip these calls if there is no tracer. */ + if (!ptrace_event_enabled(current, PTRACE_EVENT_SECCOMP)) + goto skip; + /* Allow the BPF to provide the event message */ + ptrace_event(PTRACE_EVENT_SECCOMP, data); + /* + * The delivery of a fatal signal during event + * notification may silently skip tracer notification. + * Terminating the task now avoids executing a system + * call that may not be intended. + */ + if (fatal_signal_pending(current)) + break; + return 0; case SECCOMP_RET_ALLOW: return 0; case SECCOMP_RET_KILL: