Re: [PATCHv2 perf/core 01/22] uprobes: Remove breakpoint in unapply_uprobe under mmap_write_lock
From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Date: 2025-05-19 23:48:51
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On Thu, 15 May 2025 14:10:58 +0200 Jiri Olsa [off-list ref] wrote:
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.
So, this is a bugfix, right? Thanks,
quoted hunk ↗ jump to hunk
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; }-- 2.49.0
-- Masami Hiramatsu (Google) [off-list ref]