diff mbox series

[v8,4/5] x86/pkeys: Restore altstack access in sigreturn()

Message ID 20240802061318.2140081-5-aruna.ramakrishna@oracle.com (mailing list archive)
State New
Headers show
Series x86/pkeys: update PKRU to enable all pkeys before XSAVE | expand

Commit Message

Aruna Ramakrishna Aug. 2, 2024, 6:13 a.m. UTC 
A process can disable access to the alternate signal stack by not
enabling the altstack's pkey in the PKRU register. Nevertheless, the
kernel updates the PKRU temporarily for signal handling. However, in
sigreturn(), restore_sigcontext() will restore the PKRU to the
user-defined PKRU value. This will cause restore_altstack() to fail with
a SIGSEGV as it needs read access to the altstack which is prohibited
by the user-defined PKRU value.

Fix this by restoring altstack before restoring PKRU.

Signed-off-by: Aruna Ramakrishna <aruna.ramakrishna@oracle.com>
---
 arch/x86/kernel/signal_64.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)
diff mbox series

Patch

diff --git a/arch/x86/kernel/signal_64.c b/arch/x86/kernel/signal_64.c
index 8a94053c5444..ee9453891901 100644
--- a/arch/x86/kernel/signal_64.c
+++ b/arch/x86/kernel/signal_64.c
@@ -260,13 +260,13 @@  SYSCALL_DEFINE0(rt_sigreturn)
 
 	set_current_blocked(&set);
 
-	if (!restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags))
+	if (restore_altstack(&frame->uc.uc_stack))
 		goto badframe;
 
-	if (restore_signal_shadow_stack())
+	if (!restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags))
 		goto badframe;
 
-	if (restore_altstack(&frame->uc.uc_stack))
+	if (restore_signal_shadow_stack())
 		goto badframe;
 
 	return regs->ax;