diff mbox series

[v7,15/22] powerpc/book3s64/kuap: Restrict access to userspace based on userspace AMR

Message ID 20201127044424.40686-16-aneesh.kumar@linux.ibm.com (mailing list archive)
State Accepted
Commit 4d6c551e9f548f7675a01eff229d09ab41162a25
Headers show
Series Kernel userspace access/execution prevention with hash translation | expand

Checks

Context Check Description
snowpatch_ozlabs/apply_patch success Successfully applied on branch powerpc/merge (4c202167192a77481310a3cacae9f12618b92216)
snowpatch_ozlabs/checkpatch warning total: 0 errors, 1 warnings, 0 checks, 23 lines checked
snowpatch_ozlabs/needsstable success Patch has no Fixes tags

Commit Message

Aneesh Kumar K V Nov. 27, 2020, 4:44 a.m. UTC 
If an application has configured address protection such that read/write is
denied using pkey even the kernel should receive a FAULT on accessing the same.

This patch use user AMR value stored in pt_regs.amr to achieve the same.

Reviewed-by: Sandipan Das <sandipan@linux.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
---
 arch/powerpc/include/asm/book3s/64/kup.h | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)
diff mbox series

Patch

diff --git a/arch/powerpc/include/asm/book3s/64/kup.h b/arch/powerpc/include/asm/book3s/64/kup.h
index 97e81fd820be..a417b151cff7 100644
--- a/arch/powerpc/include/asm/book3s/64/kup.h
+++ b/arch/powerpc/include/asm/book3s/64/kup.h
@@ -312,14 +312,20 @@  bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write)
 static __always_inline void allow_user_access(void __user *to, const void __user *from,
 					      unsigned long size, unsigned long dir)
 {
+	unsigned long thread_amr = 0;
+
 	// This is written so we can resolve to a single case at build time
 	BUILD_BUG_ON(!__builtin_constant_p(dir));
+
+	if (mmu_has_feature(MMU_FTR_PKEY))
+		thread_amr = current_thread_amr();
+
 	if (dir == KUAP_READ)
-		set_kuap(AMR_KUAP_BLOCK_WRITE);
+		set_kuap(thread_amr | AMR_KUAP_BLOCK_WRITE);
 	else if (dir == KUAP_WRITE)
-		set_kuap(AMR_KUAP_BLOCK_READ);
+		set_kuap(thread_amr | AMR_KUAP_BLOCK_READ);
 	else if (dir == KUAP_READ_WRITE)
-		set_kuap(0);
+		set_kuap(thread_amr);
 	else
 		BUILD_BUG();
 }