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SubjectRe: [PATCH -mm 2/4] ptrace: compat_ptrace_request siginfo
On Thu, Mar 13, 2008 at 01:32:43AM -0700, Roland McGrath wrote:
> On powerpc, this fixes a longstanding regression of 32-bit ptrace
> calls on 64-bit kernels vs native calls (64-bit calls or 32-bit
> kernels). This can be seen in a 32-bit call using PTRACE_GETSIGINFO
> to examine e.g. siginfo_t.si_addr from a signal that sets it.
> (This was broken as of 2.6.24 and, I presume, many or all prior versions.)

BTW, this also fixes a long-standing bug in x86_64 ptrace32_siginfo:

ret = sys_ptrace(request, pid, addr, (unsigned long)si);
if (ret)
return ret;
if (request == PTRACE_GETSIGINFO) {
if (copy_from_user(&ssi, si, sizeof(siginfo_t)))
return -EFAULT;
ret = copy_siginfo_to_user32(si32, &ssi);
}

si comes back with the upper bits of si_code missing, courtesy of
copy_siginfo_to_user:

err |= __put_user((short)from->si_code, &to->si_code);

causing copy_siginfo_to_user32 to not copy any fields of the union
past the first word because the upper 16 bits are used to figure out
what needs copying.

Jeff

--
Work email - jdike at linux dot intel dot com


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