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

[Andrii Nakryiko]

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().

Fixes: da1816b1caec ("uprobes: Teach handler_chain() to filter out the probed 
task")
Signed-off-by: Andrii Nakryiko <and...@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