linux-kernel - [PATCH RESEND v3 1/6] powerpc/signal64: Access function descriptor with user access block

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Message-Id: <1718f38859d5366f82d5bef531f255cedf537b5d.1631537060.git.christophe.leroy@csgroup.eu>
Date:   Mon, 13 Sep 2021 17:19:05 +0200
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>, ebiederm@...ssion.com,
        hch@...radead.org
Cc:     Christophe Leroy <christophe.leroy@...roup.eu>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH RESEND v3 1/6] 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>
---
Resending with correct date, sorry for the noise, my new PC seems to have used the fake date from Git instead of adding proper Date: from current date/time.


v3: Flatten the change to avoid nested gotos.
---
 arch/powerpc/kernel/signal_64.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
index 1831bba0582e..7b1cd50bc4fb 100644
--- a/arch/powerpc/kernel/signal_64.c
+++ b/arch/powerpc/kernel/signal_64.c
@@ -936,8 +936,13 @@ 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)))
+			goto badfunc;
+
+		unsafe_get_user(regs->ctr, &funct_desc_ptr->entry, badfunc_block);
+		unsafe_get_user(regs->gpr[2], &funct_desc_ptr->toc, badfunc_block);
+
+		user_read_access_end();
 	}
 
 	/* enter the signal handler in native-endian mode */
@@ -962,5 +967,12 @@ int handle_rt_signal64(struct ksignal *ksig, sigset_t *set,
 badframe:
 	signal_fault(current, regs, "handle_rt_signal64", frame);
 
+	return 1;
+
+badfunc_block:
+	user_read_access_end();
+badfunc:
+	signal_fault(current, regs, __func__, (void __user *)ksig->ka.sa.sa_handler);
+
 	return 1;
 }
-- 
2.31.1