linux-kernel - [PATCHv2 perf/core 01/22] uprobes: Remove breakpoint in unapply_uprobe under mmap_write

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Message-ID: <20250515121121.2332905-2-jolsa@kernel.org>
Date: Thu, 15 May 2025 14:10:58 +0200
From: Jiri Olsa <jolsa@...nel.org>
To: Oleg Nesterov <oleg@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrii Nakryiko <andrii@...nel.org>
Cc: bpf@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org,
	x86@...nel.org,
	Song Liu <songliubraving@...com>,
	Yonghong Song <yhs@...com>,
	John Fastabend <john.fastabend@...il.com>,
	Hao Luo <haoluo@...gle.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Alan Maguire <alan.maguire@...cle.com>,
	David Laight <David.Laight@...LAB.COM>,
	Thomas Weißschuh <thomas@...ch.de>,
	Ingo Molnar <mingo@...nel.org>
Subject: [PATCHv2 perf/core 01/22] uprobes: Remove breakpoint in unapply_uprobe under mmap_write_lock

Currently unapply_uprobe takes mmap_read_lock, but it might call
remove_breakpoint which eventually changes user pages.

Current code writes either breakpoint or original instruction, so
it can probably go away with that, but with the upcoming change that
writes multiple instructions on the probed address we need to ensure
that any update to mm's pages is exclusive.

Signed-off-by: Jiri Olsa <jolsa@...nel.org>
---
 kernel/events/uprobes.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 84ee7b590861..257581432cd8 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -483,7 +483,7 @@ static int __uprobe_write_opcode(struct vm_area_struct *vma,
  * @opcode_vaddr: the virtual address to store the opcode.
  * @opcode: opcode to be written at @opcode_vaddr.
  *
- * Called with mm->mmap_lock held for read or write.
+ * Called with mm->mmap_lock held for write.
  * Return 0 (success) or a negative errno.
  */
 int uprobe_write_opcode(struct arch_uprobe *auprobe, struct vm_area_struct *vma,
@@ -1464,7 +1464,7 @@ static int unapply_uprobe(struct uprobe *uprobe, struct mm_struct *mm)
 	struct vm_area_struct *vma;
 	int err = 0;
 
-	mmap_read_lock(mm);
+	mmap_write_lock(mm);
 	for_each_vma(vmi, vma) {
 		unsigned long vaddr;
 		loff_t offset;
@@ -1481,7 +1481,7 @@ static int unapply_uprobe(struct uprobe *uprobe, struct mm_struct *mm)
 		vaddr = offset_to_vaddr(vma, uprobe->offset);
 		err |= remove_breakpoint(uprobe, vma, vaddr);
 	}
-	mmap_read_unlock(mm);
+	mmap_write_unlock(mm);
 
 	return err;
 }
-- 
2.49.0