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uprobes: Remove breakpoint in unapply_uprobe under mmap_write_lock

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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/

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Link: https://lore.kernel.org/r/20250720112133.244369-2-jolsa@kernel.org
This commit is contained in:
Jiri Olsa
2025-07-20 13:21:11 +02:00
committed by Peter Zijlstra
parent 448f97fba9
commit 7769cb177b
1 changed files with 3 additions and 3 deletions
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6
kernel/events/uprobes.c
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@@ -482,7 +482,7 @@ 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,
@@ -1463,7 +1463,7 @@ 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;
@@ -1480,7 +1480,7 @@ 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;
}