linux-kernel - [PATCH 5.9 047/391] powerpc/watchpoint/ptrace: Fix SETHWDEBUG when CONFIG_HAVE_HW

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Date:   Tue,  3 Nov 2020 21:31:38 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Pedro Miraglia Franco de Carvalho <pedromfc@...ux.ibm.com>,
        Ravi Bangoria <ravi.bangoria@...ux.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.9 047/391] powerpc/watchpoint/ptrace: Fix SETHWDEBUG when CONFIG_HAVE_HW_BREAKPOINT=N

From: Ravi Bangoria <ravi.bangoria@...ux.ibm.com>

[ Upstream commit 9b6b7c680cc20971444d9f836e49fc98848bcd0a ]

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 accesses user memory.

Reported-by: Pedro Miraglia Franco de Carvalho <pedromfc@...ux.ibm.com>
Suggested-by: Pedro Miraglia Franco de Carvalho <pedromfc@...ux.ibm.com>
Signed-off-by: Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Link: https://lore.kernel.org/r/20200902042945.129369-4-ravi.bangoria@linux.ibm.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 8bd8d8de5c40b..a570782e954be 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;
 	brk.hw_len = DABR_MAX_LEN;
 	if (bp_info->trigger_type & PPC_BREAKPOINT_TRIGGER_READ)
-- 
2.27.0