Re: [PATCH 02/12] uprobes: grab write mmap lock in unapply_uprobe()

[Masami Hiramatsu (Google) <mhiramat@kernel.org>]

On Mon, 24 Jun 2024 17:21:34 -0700
Andrii Nakryiko <andrii@kernel.org> wrote:

> Given unapply_uprobe() can call remove_breakpoint() which eventually
> calls uprobe_write_opcode(), which can modify a set of memory pages and
> expects mm->mmap_lock held for write, it needs to have writer lock.
> 
> Fix this by switching to mmap_write_lock()/mmap_write_unlock().
> 

Oops, it is an actual bug, right?

Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Thanks,

> Fixes: da1816b1caec ("uprobes: Teach handler_chain() to filter out the probed task")
> Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
> ---
>  kernel/events/uprobes.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index 197fbe4663b5..e896eeecb091 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -1235,7 +1235,7 @@ 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;
> @@ -1252,7 +1252,7 @@ static int unapply_uprobe(struct uprobe *uprobe, struct mm_struct *mm)
>  		vaddr = offset_to_vaddr(vma, uprobe->offset);
>  		err |= remove_breakpoint(uprobe, mm, vaddr);
>  	}
> -	mmap_read_unlock(mm);
> +	mmap_write_unlock(mm);
>  
>  	return err;
>  }
> -- 
> 2.43.0
> 


-- 
Masami Hiramatsu (Google) <mhiramat@kernel.org>