linux-kernel - [PATCH v2] uprobes: fix kernel info leak via "[uprobes]" vma

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Message-ID: <20240929162047.GA12611@redhat.com>
Date: Sun, 29 Sep 2024 18:20:47 +0200
From: Oleg Nesterov <oleg@...hat.com>
To: Masami Hiramatsu <mhiramat@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>
Cc: Catalin Marinas <catalin.marinas@....com>,
	"Liao, Chang" <liaochang1@...wei.com>,
	Will Deacon <will@...nel.org>, linux-kernel@...r.kernel.org
Subject: [PATCH v2] uprobes: fix kernel info leak via "[uprobes]" vma

xol_add_vma() maps the uninitialized page allocated by __create_xol_area()
into userspace. On some architectures (x86) this memory is readable even
without VM_READ, VM_EXEC results in the same pgprot_t as VM_EXEC|VM_READ,
although this doesn't really matter, debugger can read this memory anyway.

Reported-by: Will Deacon <will@...nel.org>
Fixes: d4b3b6384f98 ("uprobes/core: Allocate XOL slots for uprobes use")
Cc: stable@...r.kernel.org
Acked-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
Signed-off-by: Oleg Nesterov <oleg@...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 2ec796e2f055..4b52cb2ae6d6 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1545,7 +1545,7 @@ static struct xol_area *__create_xol_area(unsigned long vaddr)
 	if (!area->bitmap)
 		goto free_area;
 
-	area->page = alloc_page(GFP_HIGHUSER);
+	area->page = alloc_page(GFP_HIGHUSER | __GFP_ZERO);
 	if (!area->page)
 		goto free_bitmap;
 
-- 
2.25.1.362.g51ebf55