linux-kernel - [PATCH v1] uprobes: use pagesize-aligned virtual address when replacing pages

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Date: Mon, 15 Jan 2024 11:07:31 +0100
From: David Hildenbrand <david@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: linux-mm@...ck.org,
	linux-perf-users@...r.kernel.org,
	David Hildenbrand <david@...hat.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Ryan Roberts <ryan.roberts@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Namhyung Kim <namhyung@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>
Subject: [PATCH v1] uprobes: use pagesize-aligned virtual address when replacing pages

uprobes passes an unaligned page mapping address to
folio_add_new_anon_rmap(), which ends up triggering a VM_BUG_ON() we
recently extended in commit 372cbd4d5a066 ("mm: non-pmd-mappable, large
folios for folio_add_new_anon_rmap()").

Arguably, this is uprobes code doing something wrong; however,
for the time being it would have likely worked in rmap code because
__folio_set_anon() would set folio->index to the same value.

Looking at __replace_page(), we'd also pass slightly wrong values to
mmu_notifier_range_init(), page_vma_mapped_walk(), flush_cache_page(),
ptep_clear_flush() and set_pte_at_notify(). I suspect most of them are
fine, but let's just mark the introducing commit as the one needed
fixing. I don't think CC stable is warranted.

We'll add more sanity checks in rmap code separately, to make sure that
we always get properly aligned addresses.

Reported-by: Jiri Olsa <jolsa@...nel.org>
Closes: https://lkml.kernel.org/r/ZaMR2EWN-HvlCfUl@krava
Fixes: c517ee744b96 ("uprobes: __replace_page() should not use page_address_in_vma()")
Tested-by: Jiri Olsa <jolsa@...nel.org>
Reviewed-by: Ryan Roberts <ryan.roberts@....com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Mark Rutland <mark.rutland@....com>
Cc: Alexander Shishkin
Cc: Jiri Olsa <jolsa@...nel.org>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Ian Rogers <irogers@...gle.com>
Cc: Adrian Hunter <adrian.hunter@...el.com>
Signed-off-by: David Hildenbrand <david@...hat.com>
---
 kernel/events/uprobes.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 485bb0389b488..929e98c629652 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -537,7 +537,7 @@ int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm,
 		}
 	}
 
-	ret = __replace_page(vma, vaddr, old_page, new_page);
+	ret = __replace_page(vma, vaddr & PAGE_MASK, old_page, new_page);
 	if (new_page)
 		put_page(new_page);
 put_old:
-- 
2.43.0