6.5-stable review patch. If anyone has any objections, please let me know.
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From: Björn Töpel bjorn@rivosinc.com
commit 9f564b92cf6d0ecb398f9348600a7d8a7f8ea804 upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/riscv/include/asm/kprobes.h | 9 +++++++++ arch/riscv/include/asm/uprobes.h | 11 +++++++++++ arch/riscv/kernel/traps.c | 28 ++++++++++++++++++---------- 3 files changed, 38 insertions(+), 10 deletions(-)
--- 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 */ --- 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 */ --- 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> @@ -246,22 +248,28 @@ static inline unsigned long get_break_in 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))