linux-kernel - [PATCH v4 1/6] powerpc/watchpoint/ptrace: Fix SETHWDEBUG when CONFIG_HAVE_HW

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Message-Id: <20200817102330.777537-2-ravi.bangoria@linux.ibm.com>
Date:   Mon, 17 Aug 2020 15:53:25 +0530
From:   Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
To:     mpe@...erman.id.au, christophe.leroy@....fr
Cc:     ravi.bangoria@...ux.ibm.com, mikey@...ling.org, paulus@...ba.org,
        naveen.n.rao@...ux.vnet.ibm.com, pedromfc@...ibm.com,
        rogealve@...ibm.com, jniethe5@...il.com,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: [PATCH v4 1/6] powerpc/watchpoint/ptrace: Fix SETHWDEBUG when CONFIG_HAVE_HW_BREAKPOINT=N

When kernel is compiled with CONFIG_HAVE_HW_BREAKPOINT=N, user can
still create watchpoint using PPC_PTRACE_SETHWDEBUG, with limited
functionalities. But, such watchpoints are never firing because of
the missing privilege settings. Fix that.

It's safe to set HW_BRK_TYPE_PRIV_ALL because we don't really leak
any kernel address in signal info. Setting HW_BRK_TYPE_PRIV_ALL will
also help to find scenarios when kernel corrupts user memory.

Reported-by: Pedro Miraglia Franco de Carvalho <pedromfc@...ibm.com>
Suggested-by: Pedro Miraglia Franco de Carvalho <pedromfc@...ibm.com>
Signed-off-by: Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
---
 arch/powerpc/kernel/ptrace/ptrace-noadv.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/ptrace/ptrace-noadv.c b/arch/powerpc/kernel/ptrace/ptrace-noadv.c
index 697c7e4b5877..57a0ab822334 100644
--- a/arch/powerpc/kernel/ptrace/ptrace-noadv.c
+++ b/arch/powerpc/kernel/ptrace/ptrace-noadv.c
@@ -217,7 +217,7 @@ long ppc_set_hwdebug(struct task_struct *child, struct ppc_hw_breakpoint *bp_inf
 		return -EIO;
 
 	brk.address = ALIGN_DOWN(bp_info->addr, HW_BREAKPOINT_SIZE);
-	brk.type = HW_BRK_TYPE_TRANSLATE;
+	brk.type = HW_BRK_TYPE_TRANSLATE | HW_BRK_TYPE_PRIV_ALL;
 	brk.len = DABR_MAX_LEN;
 	if (bp_info->trigger_type & PPC_BREAKPOINT_TRIGGER_READ)
 		brk.type |= HW_BRK_TYPE_READ;
-- 
2.26.2