[PATCH v3] riscv: Only consider swbp/ss handlers for correct privileged mode
flat view
STALE1111d
LANDED: 4 (2M)
From: Björn Töpel <bjorn@kernel.org>
Date: 2023-09-12 06:56:37
Also in:
linux-riscv, lkml
Subsystem:
risc-v architecture, the rest, uprobes · Maintainers:
Paul Walmsley, Palmer Dabbelt, Albert Ou, Linus Torvalds, Masami Hiramatsu, Oleg Nesterov, Peter Zijlstra
3 review trailers; landed in mainline as 9f564b92cf6d on 2023-09-20.
From: Björn Töpel <redacted>
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/ (local) # [1]
Fixes: 74784081aac8 ("riscv: Add uprobes supported")
Reviewed-by: Guo Ren <guoren@kernel.org>
Reviewed-by: Nam Cao <redacted>
Tested-by: Puranjay Mohan <redacted>
Signed-off-by: Björn Töpel <redacted>
---
v2->v3: Remove incorrect tags (Conor)
Collect review/test tags
v1->v2: Fix Clang build warning (kernel test robot)
---
arch/riscv/include/asm/kprobes.h | 11 ++++++++++-
arch/riscv/include/asm/uprobes.h | 13 ++++++++++++-
arch/riscv/kernel/traps.c | 28 ++++++++++++++++++----------
3 files changed, 40 insertions(+), 12 deletions(-)
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))
base-commit: 0bb80ecc33a8fb5a682236443c1e740d5c917d1d -- 2.39.2