linux-kernel - [PATCH 3/7] powerpc/signal64: Access function descriptor with user access block

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Date:   Tue, 15 Jun 2021 06:40:59 +0000 (UTC)
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH 3/7] powerpc/signal64: Access function descriptor with user
 access block

Access the function descriptor of the handler within a
user access block.

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 arch/powerpc/kernel/signal_64.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
index 8b2eb758131c..9ca97b4366df 100644
--- a/arch/powerpc/kernel/signal_64.c
+++ b/arch/powerpc/kernel/signal_64.c
@@ -936,8 +936,18 @@ int handle_rt_signal64(struct ksignal *ksig, sigset_t *set,
 		func_descr_t __user *funct_desc_ptr =
 			(func_descr_t __user *) ksig->ka.sa.sa_handler;
 
-		err |= get_user(regs->ctr, &funct_desc_ptr->entry);
-		err |= get_user(regs->gpr[2], &funct_desc_ptr->toc);
+		if (user_read_access_begin(funct_desc_ptr, sizeof(func_descr_t))) {
+			unsafe_get_user(regs->ctr, &funct_desc_ptr->entry, bad_funct_desc_block);
+			unsafe_get_user(regs->gpr[2], &funct_desc_ptr->toc, bad_funct_desc_block);
+		} else {
+			goto bad_funct_desc;
+bad_funct_desc_block:
+			user_read_access_end();
+bad_funct_desc:
+			signal_fault(current, regs, __func__, funct_desc_ptr);
+			return 1;
+		}
+		user_read_access_end();
 	}
 
 	/* enter the signal handler in native-endian mode */
-- 
2.25.0