uprobes: fix kernel info leak via "[uprobes]" vma

commit 34820304cc2cd1804ee1f8f3504ec77813d29c8e upstream.

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.

Link: https://lore.kernel.org/all/20240929162047.GA12611@redhat.com/
Reported-by: Will Deacon <will@kernel.org>
Fixes: d4b3b6384f98 ("uprobes/core: Allocate XOL slots for uprobes use")
Cc: stable@vger.kernel.org
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 28c678c8daef3696b18d669fabc055b465806afb..3dd1f146436480496e2c910a92f85ae3ff5dcfc5 100644 (file)
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1491,7 +1491,7 @@ static struct xol_area *__create_xol_area(unsigned long vaddr)
 
        area->xol_mapping.name = "[uprobes]";
        area->xol_mapping.pages = area->pages;
-       area->pages[0] = alloc_page(GFP_HIGHUSER);
+       area->pages[0] = alloc_page(GFP_HIGHUSER | __GFP_ZERO);
        if (!area->pages[0])
                goto free_bitmap;
        area->pages[1] = NULL;