[PATCHv4 perf/core 01/22] uprobes: Remove breakpoint in unapply_uprobe under mmap_write_lock
From: Jiri Olsa <jolsa@kernel.org>
Date: 2025-07-08 13:24:00
Also in:
bpf, lkml
Subsystem:
performance events subsystem, the rest, uprobes · Maintainers:
Peter Zijlstra, Ingo Molnar, Arnaldo Carvalho de Melo, Namhyung Kim, Linus Torvalds, Masami Hiramatsu, Oleg Nesterov
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 go away with read lock as explained in here [1]. 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. [1] https://lore.kernel.org/all/20240710140045.GA1084@redhat.com/ (local) Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Jiri Olsa <jolsa@kernel.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; }
--
2.50.0