The patch below does not apply to the 6.1-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y git checkout FETCH_HEAD git cherry-pick -x 9f564b92cf6d0ecb398f9348600a7d8a7f8ea804 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2023101500-bubbly-batboy-9184@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..
Possible dependencies:
9f564b92cf6d ("riscv: Only consider swbp/ss handlers for correct privileged mode") f0bddf50586d ("riscv: entry: Convert to generic entry") c3ec1e8964fb ("Merge patch series "RISC-V: Align the shadow stack"")
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 9f564b92cf6d0ecb398f9348600a7d8a7f8ea804 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Bj=C3=B6rn=20T=C3=B6pel?= bjorn@rivosinc.com Date: Tue, 12 Sep 2023 08:56:19 +0200 Subject: [PATCH] riscv: Only consider swbp/ss handlers for correct privileged mode MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit
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.... # [1] Fixes: 74784081aac8 ("riscv: Add uprobes supported") Reviewed-by: Guo Ren guoren@kernel.org Reviewed-by: Nam Cao namcaov@gmail.com Tested-by: Puranjay Mohan puranjay12@gmail.com Signed-off-by: Björn Töpel bjorn@rivosinc.com Link: https://lore.kernel.org/r/20230912065619.62020-1-bjorn@kernel.org Signed-off-by: Palmer Dabbelt palmer@rivosinc.com
diff --git a/arch/riscv/include/asm/kprobes.h b/arch/riscv/include/asm/kprobes.h index e7882ccb0fd4..78ea44f76718 100644 --- a/arch/riscv/include/asm/kprobes.h +++ b/arch/riscv/include/asm/kprobes.h @@ -40,6 +40,15 @@ void arch_remove_kprobe(struct kprobe *p); int kprobe_fault_handler(struct pt_regs *regs, unsigned int trapnr); bool kprobe_breakpoint_handler(struct pt_regs *regs); bool kprobe_single_step_handler(struct pt_regs *regs); - +#else +static inline bool kprobe_breakpoint_handler(struct pt_regs *regs) +{ + return false; +} + +static inline bool kprobe_single_step_handler(struct pt_regs *regs) +{ + return false; +} #endif /* CONFIG_KPROBES */ #endif /* _ASM_RISCV_KPROBES_H */ diff --git a/arch/riscv/include/asm/uprobes.h b/arch/riscv/include/asm/uprobes.h index f2183e00fdd2..3fc7deda9190 100644 --- a/arch/riscv/include/asm/uprobes.h +++ b/arch/riscv/include/asm/uprobes.h @@ -34,7 +34,18 @@ struct arch_uprobe { bool simulate; };
+#ifdef CONFIG_UPROBES bool uprobe_breakpoint_handler(struct pt_regs *regs); bool uprobe_single_step_handler(struct pt_regs *regs); - +#else +static inline bool uprobe_breakpoint_handler(struct pt_regs *regs) +{ + return false; +} + +static inline bool uprobe_single_step_handler(struct pt_regs *regs) +{ + return false; +} +#endif /* CONFIG_UPROBES */ #endif /* _ASM_RISCV_UPROBES_H */ diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c index 19807c4d3805..fae8f610d867 100644 --- a/arch/riscv/kernel/traps.c +++ b/arch/riscv/kernel/traps.c @@ -13,6 +13,8 @@ #include <linux/kdebug.h> #include <linux/uaccess.h> #include <linux/kprobes.h> +#include <linux/uprobes.h> +#include <asm/uprobes.h> #include <linux/mm.h> #include <linux/module.h> #include <linux/irq.h> @@ -247,22 +249,28 @@ static inline unsigned long get_break_insn_length(unsigned long pc) return GET_INSN_LENGTH(insn); }
+static bool probe_single_step_handler(struct pt_regs *regs) +{ + bool user = user_mode(regs); + + return user ? uprobe_single_step_handler(regs) : kprobe_single_step_handler(regs); +} + +static bool probe_breakpoint_handler(struct pt_regs *regs) +{ + bool user = user_mode(regs); + + return user ? uprobe_breakpoint_handler(regs) : kprobe_breakpoint_handler(regs); +} + void handle_break(struct pt_regs *regs) { -#ifdef CONFIG_KPROBES - if (kprobe_single_step_handler(regs)) + if (probe_single_step_handler(regs)) return;
- if (kprobe_breakpoint_handler(regs)) - return; -#endif -#ifdef CONFIG_UPROBES - if (uprobe_single_step_handler(regs)) + if (probe_breakpoint_handler(regs)) return;
- if (uprobe_breakpoint_handler(regs)) - return; -#endif current->thread.bad_cause = regs->cause;
if (user_mode(regs))