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Kernel+strace: Remove unnecessary indirection for PEEK

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Also, remove incomplete, superfluous check.
Incomplete, because only the byte at the provided address was checked;
this misses the last bytes of the "jerk page".
Superfluous, because it is already correctly checked by peek_user_data
(which calls copy_from_user).

The caller/tracer should not typically attempt to read non-userspace
addresses, we don't need to "hot-path" it either.
This commit is contained in:
Ben Wiederhake 2021-11-25 20:15:02 +01:00 • committed by Andreas Kling
parent 6f37510a71
commit 3e223185b3
3 changed files with 5 additions and 21 deletions
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5
Kernel/API/Syscall.h
View file

@ -465,11 +465,6 @@ struct SC_ptrace_params {
FlatPtr data;
};
struct SC_ptrace_peek_params {
const void* address;
FlatPtr* out_data;
};
struct SC_set_coredump_metadata_params {
StringArgument key;
StringArgument value;

16
Kernel/Syscalls/ptrace.cpp
View file

@ -114,26 +114,18 @@ static ErrorOr<FlatPtr> handle_ptrace(const Kernel::Syscall::SC_ptrace_params& p
}
case PT_PEEK: {
Kernel::Syscall::SC_ptrace_peek_params peek_params {};
TRY(copy_from_user(&peek_params, reinterpret_cast<Kernel::Syscall::SC_ptrace_peek_params*>(params.addr)));
if (!Memory::is_user_address(VirtualAddress { peek_params.address }))
return EFAULT;
auto data = TRY(peer->process().peek_user_data(Userspace<const FlatPtr*> { (FlatPtr)peek_params.address }));
TRY(copy_to_user(peek_params.out_data, &data));
auto data = TRY(peer->process().peek_user_data(Userspace<const FlatPtr*> { (FlatPtr)params.addr }));
TRY(copy_to_user((FlatPtr*)params.data, &data));
break;
}
case PT_POKE:
if (!Memory::is_user_address(VirtualAddress { params.addr }))
return EFAULT;
TRY(peer->process().poke_user_data(Userspace<FlatPtr*> { (FlatPtr)params.addr }, params.data));
return 0;
case PT_PEEKDEBUG: {
Kernel::Syscall::SC_ptrace_peek_params peek_params {};
TRY(copy_from_user(&peek_params, reinterpret_cast<Kernel::Syscall::SC_ptrace_peek_params*>(params.addr)));
auto data = TRY(peer->peek_debug_register(reinterpret_cast<uintptr_t>(peek_params.address)));
TRY(copy_to_user(peek_params.out_data, &data));
auto data = TRY(peer->peek_debug_register(reinterpret_cast<uintptr_t>(params.addr)));
TRY(copy_to_user((FlatPtr*)params.data, &data));
break;
}
case PT_POKEDEBUG:

5
Userland/Libraries/LibC/sys/ptrace.cpp
View file

@ -18,12 +18,9 @@ long ptrace(int request, pid_t tid, void* addr, void* data)
// by looking at errno rather than the return value.
FlatPtr out_data;
Syscall::SC_ptrace_peek_params peek_params;
auto is_peek_type = request == PT_PEEK || request == PT_PEEKDEBUG;
if (is_peek_type) {
peek_params.address = reinterpret_cast<FlatPtr*>(addr);
peek_params.out_data = &out_data;
addr = &peek_params;
data = &out_data;
}
Syscall::SC_ptrace_params params {