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@xxxxxxxxxx/ Acked-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx> Acked-by: Oleg Nesterov <oleg@xxxxxxxxxx> Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx> --- 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
