From: Nam Cao <namcaov@gmail.com>
To: "Björn Töpel" <bjorn@kernel.org>
Cc: "Paul Walmsley" <paul.walmsley@sifive.com>,
"Palmer Dabbelt" <palmer@dabbelt.com>,
"Albert Ou" <aou@eecs.berkeley.edu>,
linux-riscv@lists.infradead.org, "Guo Ren" <guoren@kernel.org>,
"Björn Töpel" <bjorn@rivosinc.com>,
linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
"kernel test robot" <lkp@intel.com>
Subject: Re: [PATCH v2] riscv: Only consider swbp/ss handlers for correct privileged mode
Date: Sun, 27 Aug 2023 22:35:21 +0200 [thread overview]
Message-ID: <ZOuziWaJpYV0LfB3@nam-dell> (raw)
In-Reply-To: <20230827114003.224958-1-bjorn@kernel.org>
On Sun, Aug 27, 2023 at 01:40:03PM +0200, Björn Töpel wrote:
> From: Björn Töpel <bjorn@rivosinc.com>
>
> RISC-V software breakpoint trap handlers are used for {k,u}probes.
>
> When trapping from kernelmode, only the kernelmode handlers should be
> considered. Vice versa, only usermode handlers for usermode
> traps. This is not the case on RISC-V, which can trigger a bug if a
> userspace process uses uprobes, and a WARN() is triggered from
> kernelmode (which is implemented via {c.,}ebreak).
>
> The kernel will trap on the kernelmode {c.,}ebreak, look for uprobes
> handlers, realize incorrectly that uprobes need to be handled, and
> exit the trap handler early. The trap returns to re-executing the
> {c.,}ebreak, and enter an infinite trap-loop.
>
> The issue was found running the BPF selftest [1].
>
> Fix this issue by only considering the swbp/ss handlers for
> kernel/usermode respectively. Also, move CONFIG ifdeffery from traps.c
> to the asm/{k,u}probes.h headers.
>
> Note that linux/uprobes.h only include asm/uprobes.h if CONFIG_UPROBES
> is defined, which is why asm/uprobes.h needs to be unconditionally
> included in traps.c
>
> Link: https://lore.kernel.org/linux-riscv/87v8d19aun.fsf@all.your.base.are.belong.to.us/ # [1]
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202308271841.HlnnHFL7-lkp@intel.com/
> Reviewed-by: Guo Ren <guoren@kernel.org>
> Fixes: 74784081aac8 ("riscv: Add uprobes supported")
> Signed-off-by: Björn Töpel <bjorn@rivosinc.com>
Reviewed-by: Nam Cao <namcaov@gmail.com>
Best regards,
Nam
next prev parent reply other threads:[~2023-08-27 20:36 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-27 11:40 [PATCH v2] riscv: Only consider swbp/ss handlers for correct privileged mode Björn Töpel
2023-08-27 11:44 ` Conor Dooley
2023-08-27 17:57 ` Björn Töpel
2023-08-27 20:35 ` Nam Cao [this message]
2023-08-28 15:35 ` Puranjay Mohan
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