2019-09-24 16:44:05

by Vincent Chen

Subject: [PATCH 3/4] riscv: Correct the handling of unexpected ebreak in do_trap_break()

For the kernel space, all ebreak instructions are determined at compile
time because the kernel space debugging module is currently unsupported.
Hence, it should be treated as a bug if an ebreak instruction which does
not belong to BUG_TRAP_TYPE_WARN or BUG_TRAP_TYPE_BUG is executed in
kernel space. For the userspace, debugging module or user problem may
intentionally insert an ebreak instruction to trigger a SIGTRAP signal.
To approach the above two situations, the do_trap_break() will direct
the BUG_TRAP_TYPE_NONE ebreak exception issued in kernel space to die()
and will send a SIGTRAP to the trapped process only when the ebreak is
in userspace.

Signed-off-by: Vincent Chen <[email protected]>
---
arch/riscv/kernel/traps.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
index 82f42a55451e..dd13bc90aeb6 100644
--- a/arch/riscv/kernel/traps.c
+++ b/arch/riscv/kernel/traps.c
@@ -130,8 +130,6 @@ asmlinkage void do_trap_break(struct pt_regs *regs)
type = report_bug(regs->sepc, regs);
switch (type) {
#ifdef CONFIG_GENERIC_BUG
- case BUG_TRAP_TYPE_NONE:
- break;
case BUG_TRAP_TYPE_WARN:
regs->sepc += get_break_insn_length(regs->sepc);
return;
@@ -140,8 +138,9 @@ asmlinkage void do_trap_break(struct pt_regs *regs)
default:
die(regs, "Kernel BUG");
}
- }
- force_sig_fault(SIGTRAP, TRAP_BRKPT, (void __user *)(regs->sepc));
+ } else
+ force_sig_fault(SIGTRAP, TRAP_BRKPT,
+ (void __user *)(regs->sepc));
}

#ifdef CONFIG_GENERIC_BUG
--
2.7.4

2019-09-27 22:46:13

by Christoph Hellwig

Subject: Re: [PATCH 3/4] riscv: Correct the handling of unexpected ebreak in do_trap_break()

Looks ok:

Reviewed-by: Christoph Hellwig <[email protected]>

2019-10-04 18:30:04

by Paul Walmsley

Subject: Re: [PATCH 3/4] riscv: Correct the handling of unexpected ebreak in do_trap_break()

On Mon, 23 Sep 2019, Vincent Chen wrote:

> For the kernel space, all ebreak instructions are determined at compile
> time because the kernel space debugging module is currently unsupported.
> Hence, it should be treated as a bug if an ebreak instruction which does
> not belong to BUG_TRAP_TYPE_WARN or BUG_TRAP_TYPE_BUG is executed in
> kernel space. For the userspace, debugging module or user problem may
> intentionally insert an ebreak instruction to trigger a SIGTRAP signal.
> To approach the above two situations, the do_trap_break() will direct
> the BUG_TRAP_TYPE_NONE ebreak exception issued in kernel space to die()
> and will send a SIGTRAP to the trapped process only when the ebreak is
> in userspace.
>
> Signed-off-by: Vincent Chen <[email protected]>

Thanks, queued the following for v5.4-rc.


- Paul

From: Vincent Chen <[email protected]>
Date: Mon, 23 Sep 2019 08:45:16 +0800
Subject: [PATCH] riscv: Correct the handling of unexpected ebreak in
do_trap_break()

For the kernel space, all ebreak instructions are determined at compile
time because the kernel space debugging module is currently unsupported.
Hence, it should be treated as a bug if an ebreak instruction which does
not belong to BUG_TRAP_TYPE_WARN or BUG_TRAP_TYPE_BUG is executed in
kernel space. For the userspace, debugging module or user problem may
intentionally insert an ebreak instruction to trigger a SIGTRAP signal.
To approach the above two situations, the do_trap_break() will direct
the BUG_TRAP_TYPE_NONE ebreak exception issued in kernel space to die()
and will send a SIGTRAP to the trapped process only when the ebreak is
in userspace.

Signed-off-by: Vincent Chen <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
[[email protected]: fixed checkpatch issue]
Signed-off-by: Paul Walmsley <[email protected]>
---
arch/riscv/kernel/traps.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
index 82f42a55451e..93742df9067f 100644
--- a/arch/riscv/kernel/traps.c
+++ b/arch/riscv/kernel/traps.c
@@ -130,8 +130,6 @@ asmlinkage void do_trap_break(struct pt_regs *regs)
type = report_bug(regs->sepc, regs);
switch (type) {
#ifdef CONFIG_GENERIC_BUG
- case BUG_TRAP_TYPE_NONE:
- break;
case BUG_TRAP_TYPE_WARN:
regs->sepc += get_break_insn_length(regs->sepc);
return;
@@ -140,8 +138,10 @@ asmlinkage void do_trap_break(struct pt_regs *regs)
default:
die(regs, "Kernel BUG");
}
+ } else {
+ force_sig_fault(SIGTRAP, TRAP_BRKPT,
+ (void __user *)(regs->sepc));
}
- force_sig_fault(SIGTRAP, TRAP_BRKPT, (void __user *)(regs->sepc));
}

#ifdef CONFIG_GENERIC_BUG
--
2.23.0