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FAILED: patch "[PATCH] riscv: Only consider swbp/ss handlers for correct privileged" failed to apply to 6.1-stable tree

PATCH [email protected] 1 participant 1 message Oct 15, 2023

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Stable branch RISC-V uprobes
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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 <[email protected]>.

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 '<[email protected]>' --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?= <[email protected]>
Date: Tue, 12 Sep 2023 08:56:19 +0200
Subject: [PATCH] riscv: Only consider swbp/ss handlers for correct privileged
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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/[email protected]/ # [1] open here
Fixes 74784081aac8 ("riscv: Add uprobes supported")
Reviewed-by Guo Ren <[email protected]>
Reviewed-by Nam Cao <[email protected]>
Tested-by Puranjay Mohan <[email protected]>
Signed-off-by Björn Töpel <[email protected]>
Link https://lore.kernel.org/r/[email protected] open here
Signed-off-by Palmer Dabbelt <[email protected]>
arch/riscv/include/asm/kprobes.h +10 -1
index e7882ccb0fd4..78ea44f76718 100644
@@ -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 */
arch/riscv/include/asm/uprobes.h +12 -1
index f2183e00fdd2..3fc7deda9190 100644
@@ -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 */
arch/riscv/kernel/traps.c +18 -10
index 19807c4d3805..fae8f610d867 100644
@@ -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))