diff options
| author | Michael Ellerman <mpe@ellerman.id.au> | 2015-07-23 20:21:07 +1000 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2015-07-29 11:56:13 +1000 |
| commit | e9fbe6863281b942d7eea44c6ccabc30f46ab44f (patch) | |
| tree | 396596458f5ebfbbd4905117027920a2dfda3ee7 | |
| parent | 1cb9839b73e7f2b006a1cc9452c30f15ff8b1748 (diff) | |
powerpc: Change syscall_get_nr() to return int
The documentation for syscall_get_nr() in asm-generic says:
Note this returns int even on 64-bit machines. Only 32 bits of
system call number can be meaningful. If the actual arch value
is 64 bits, this truncates to 32 bits so 0xffffffff means -1.
However our implementation was never updated to reflect this.
Generally it's not important, but there is once case where it matters.
For seccomp filter with SECCOMP_RET_TRACE, the tracer will set
regs->gpr[0] to -1 to reject the syscall. When the task is a compat
task, this means we end up with 0xffffffff in r0 because ptrace will
zero extend the 32-bit value.
If syscall_get_nr() returns an unsigned long, then a 64-bit kernel will
see a positive value in r0 and will incorrectly allow the syscall
through seccomp.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Reviewed-by: Kees Cook <keescook@chromium.org>
| -rw-r--r-- | arch/powerpc/include/asm/syscall.h | 11 |
1 files changed, 8 insertions, 3 deletions
diff --git a/arch/powerpc/include/asm/syscall.h b/arch/powerpc/include/asm/syscall.h index 8d79a87c0511..ab9f3f0a8637 100644 --- a/arch/powerpc/include/asm/syscall.h +++ b/arch/powerpc/include/asm/syscall.h @@ -22,10 +22,15 @@ extern const unsigned long sys_call_table[]; #endif /* CONFIG_FTRACE_SYSCALLS */ -static inline long syscall_get_nr(struct task_struct *task, - struct pt_regs *regs) +static inline int syscall_get_nr(struct task_struct *task, struct pt_regs *regs) { - return TRAP(regs) == 0xc00 ? regs->gpr[0] : -1L; + /* + * Note that we are returning an int here. That means 0xffffffff, ie. + * 32-bit negative 1, will be interpreted as -1 on a 64-bit kernel. + * This is important for seccomp so that compat tasks can set r0 = -1 + * to reject the syscall. + */ + return TRAP(regs) == 0xc00 ? regs->gpr[0] : -1; } static inline void syscall_rollback(struct task_struct *task, |