iv/linux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

signal/ia64: Use the generic force_sigsegv in setup_frame

Browse Source 
The ia64 handling of failure to setup a signal frame has been trying
to set overlapping fields in struct siginfo since 2.3.43.  The si_pid
and si_uid fields are stomped when the si_addr field is set.  The
si_code of SI_KERNEL indicates that si_pid and si_uid should be valid,
and that si_addr does not exist.

Being at odds with the definition of SI_KERNEL and with nothing to
indicate that this was a signal frame setup failure there is no way
for userspace to know that si_addr was filled out instead.

In practice failure to setup a signal frame is rare, and si_pid and
si_uid are always set to 0 when si_code is SI_KERNEL so I expect no
one has looked closely enough before to see this weirdness.  Further
the only difference between force_sigsegv_info and the generic
force_sigsegv other than the return code is that force_sigsegv_info
stomps the si_uid and si_pid fields.

Remove the bug and simplify the code by using force_sigsegv in this
case just like other architectures.

Fixes: 2.3.43
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: linux-ia64@vger.kernel.org
Acked-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
This commit is contained in:
Eric W. Biederman 2018-04-16 13:55:06 -05:00
parent 795a837145
commit 8b9c6b2831
1 changed files with 12 additions and 38 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

50
arch/ia64/kernel/signal.c
View File

@ -231,37 +231,6 @@ rbs_on_sig_stack (unsigned long bsp)
return (bsp - current->sas_ss_sp < current->sas_ss_size);
}
static long
force_sigsegv_info (int sig, void __user *addr)
{
unsigned long flags;
struct siginfo si;
clear_siginfo(&si);
if (sig == SIGSEGV) {
/*
* Acquiring siglock around the sa_handler-update is almost
* certainly overkill, but this isn't a
* performance-critical path and I'd rather play it safe
* here than having to debug a nasty race if and when
* something changes in kernel/signal.c that would make it
* no longer safe to modify sa_handler without holding the
* lock.
*/
spin_lock_irqsave(&current->sighand->siglock, flags);
current->sighand->action[sig - 1].sa.sa_handler = SIG_DFL;
spin_unlock_irqrestore(&current->sighand->siglock, flags);
}
si.si_signo = SIGSEGV;
si.si_errno = 0;
si.si_code = SI_KERNEL;
si.si_pid = task_pid_vnr(current);
si.si_uid = from_kuid_munged(current_user_ns(), current_uid());
si.si_addr = addr;
force_sig_info(SIGSEGV, &si, current);
return 1;
}
static long
setup_frame(struct ksignal *ksig, sigset_t *set, struct sigscratch *scr)
{
@ -295,15 +264,18 @@ setup_frame(struct ksignal *ksig, sigset_t *set, struct sigscratch *scr)
* instead so we will die with SIGSEGV.
*/
check_sp = (new_sp - sizeof(*frame)) & -STACK_ALIGN;
if (!likely(on_sig_stack(check_sp)))
return force_sigsegv_info(ksig->sig, (void __user *)
check_sp);
if (!likely(on_sig_stack(check_sp))) {
force_sigsegv(ksig->sig, current);
return 1;
}
}
}
frame = (void __user *) ((new_sp - sizeof(*frame)) & -STACK_ALIGN);
if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
return force_sigsegv_info(ksig->sig, frame);
if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame))) {
force_sigsegv(ksig->sig, current);
return 1;
}
err = __put_user(ksig->sig, &frame->arg0);
err |= __put_user(&frame->info, &frame->arg1);
@ -317,8 +289,10 @@ setup_frame(struct ksignal *ksig, sigset_t *set, struct sigscratch *scr)
err |= __save_altstack(&frame->sc.sc_stack, scr->pt.r12);
err |= setup_sigcontext(&frame->sc, set, scr);
if (unlikely(err))
return force_sigsegv_info(ksig->sig, frame);
if (unlikely(err)) {
force_sigsegv(ksig->sig, current);
return 1;
}
scr->pt.r12 = (unsigned long) frame - 16; /* new stack pointer */
scr->pt.ar_fpsr = FPSR_DEFAULT; /* reset fpsr for signal handler */