linux-hardening - [PATCH v5 8/8] lkdtm/powerpc: Fix code patching hijack test

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Date:   Tue, 13 Jul 2021 00:31:13 -0500
From:   "Christopher M. Riedl" <cmr@...ux.ibm.com>
To:     linuxppc-dev@...ts.ozlabs.org
Cc:     tglx@...utronix.de, x86@...nel.org,
        linux-hardening@...r.kernel.org, keescook@...omium.org,
        npiggin@...il.com, dja@...ens.net, peterz@...radead.org
Subject: [PATCH v5 8/8] lkdtm/powerpc: Fix code patching hijack test

Code patching on powerpc with a STRICT_KERNEL_RWX uses a userspace
address in a temporary mm on Radix now. Use __put_user() to avoid write
failures due to KUAP when attempting a "hijack" on the patching address.
__put_user() also works with the non-userspace, vmalloc-based patching
address on non-Radix MMUs.

Signed-off-by: Christopher M. Riedl <cmr@...ux.ibm.com>
---
 drivers/misc/lkdtm/perms.c | 9 ---------
 1 file changed, 9 deletions(-)

diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
index 41e87e5f9cc86..da6a34a0a49fb 100644
--- a/drivers/misc/lkdtm/perms.c
+++ b/drivers/misc/lkdtm/perms.c
@@ -262,16 +262,7 @@ static inline u32 lkdtm_read_patch_site(void)
 /* Returns True if the write succeeds */
 static inline bool lkdtm_try_write(u32 data, u32 *addr)
 {
-#ifdef CONFIG_PPC
-	__put_kernel_nofault(addr, &data, u32, err);
-	return true;
-
-err:
-	return false;
-#endif
-#ifdef CONFIG_X86_64
 	return !__put_user(data, addr);
-#endif
 }
 
 static int lkdtm_patching_cpu(void *data)
-- 
2.26.1