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[217.105.46.58]) by smtp.gmail.com with ESMTPSA id q24-20020a17090622d800b0099d804da2e9sm3770795eja.225.2023.08.27.13.35.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 27 Aug 2023 13:35:21 -0700 (PDT) Date: Sun, 27 Aug 2023 22:35:21 +0200 From: Nam Cao To: =?iso-8859-1?Q?Bj=F6rn_T=F6pel?= Cc: Paul Walmsley , Palmer Dabbelt , Albert Ou , linux-riscv@lists.infradead.org, Guo Ren , =?iso-8859-1?Q?Bj=F6rn_T=F6pel?= , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, kernel test robot Subject: Re: [PATCH v2] riscv: Only consider swbp/ss handlers for correct privileged mode Message-ID: References: <20230827114003.224958-1-bjorn@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20230827114003.224958-1-bjorn@kernel.org> Precedence: bulk List-ID: X-Mailing-List: linux-trace-kernel@vger.kernel.org On Sun, Aug 27, 2023 at 01:40:03PM +0200, Björn Töpel wrote: > From: Björn Töpel > > 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 > Closes: https://lore.kernel.org/oe-kbuild-all/202308271841.HlnnHFL7-lkp@intel.com/ > Reviewed-by: Guo Ren > Fixes: 74784081aac8 ("riscv: Add uprobes supported") > Signed-off-by: Björn Töpel Reviewed-by: Nam Cao Best regards, Nam