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ptrace: Report error in PT_PEEK via errno

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The syscall wrapper for ptrace needs to return the peeked value when
using  PT_PEEK.
Because of this, the user has to check errno to detect an error in
PT_PEEK.

This commit changes the actual syscall's interface (only for PT_PEEK) to
allow the syscall wrapper to detect an error and change errno.
This commit is contained in:
Itamar 2020-04-10 17:34:31 +03:00 • committed by Andreas Kling
parent aae3f7b914
commit 50fd2cabff
Notes: sideshowbarker 2024-07-19 07:38:57 +09:00
3 changed files with 47 additions and 3 deletions
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20
Kernel/Ptrace.cpp
View file

@ -92,8 +92,10 @@ KResultOr<u32> handle_syscall(const Kernel::Syscall::SC_ptrace_params& params, P
auto& peer_saved_registers = peer->get_register_dump_from_stack();
// Verify that the saved registers are in usermode context
if ((peer_saved_registers.cs & 0x03) != 3)
if ((peer_saved_registers.cs & 0x03) != 3) {
return -EFAULT;
}
{
SmapDisabler disabler;
PtraceRegisters* regs = reinterpret_cast<PtraceRegisters*>(params.addr);
@ -104,12 +106,24 @@ KResultOr<u32> handle_syscall(const Kernel::Syscall::SC_ptrace_params& params, P
}
case PT_PEEK: {
u32* addr = reinterpret_cast<u32*>(params.addr);
return peer->process().peek_user_data(addr);
Kernel::Syscall::SC_ptrace_peek_params peek_params;
if (!caller.validate_read_and_copy_typed(&peek_params, reinterpret_cast<Kernel::Syscall::SC_ptrace_peek_params*>(params.addr)))
return -EFAULT;
// read validation is done inside 'peek_user_data'
auto result = peer->process().peek_user_data(peek_params.address);
if (result.is_error())
return -EFAULT;
peer->process().validate_write(peek_params.out_data, sizeof(u32));
{
SmapDisabler disabler;
*(peek_params.out_data) = result.value();
}
break;
}
case PT_POKE: {
u32* addr = reinterpret_cast<u32*>(params.addr);
// write validation is done inside 'poke_user_data'
return peer->process().poke_user_data(addr, params.data);
}

5
Kernel/Syscall.h
View file

@ -432,6 +432,11 @@ struct SC_ptrace_params {
int data;
};
struct SC_ptrace_peek_params {
u32* address;
u32* out_data;
};
void initialize();
int sync();

25
Libraries/LibC/sys/ptrace.cpp
View file

@ -24,6 +24,7 @@
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <AK/LogStream.h>
#include <Kernel/Syscall.h>
#include <errno.h>
#include <sys/ptrace.h>
@ -32,6 +33,20 @@ extern "C" {
int ptrace(int request, pid_t pid, void* addr, int data)
{
// PT_PEEK needs special handling since the syscall wrapper
// returns the peeked value as an int, which can be negative because of the cast.
// When using PT_PEEK, the user can check if an error occured
// by looking at errno rather than the return value.
u32 out_data;
Syscall::SC_ptrace_peek_params peek_params;
if (request == PT_PEEK) {
peek_params.address = reinterpret_cast<u32*>(addr);
peek_params.out_data = &out_data;
addr = &peek_params;
}
Syscall::SC_ptrace_params params {
request,
pid,
@ -39,6 +54,16 @@ int ptrace(int request, pid_t pid, void* addr, int data)
data
};
int rc = syscall(SC_ptrace, &params);
if (request == PT_PEEK) {
if (rc < 0) {
errno = -rc;
return -1;
}
errno = 0;
return static_cast<int>(out_data);
}
__RETURN_WITH_ERRNO(rc, rc, -1);
}
}