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.

Link: https://lore.kernel.org/all/[email protected]/
Reported-by: Will Deacon <[email protected]>
Fixes: d4b3b6384f98 ("uprobes/core: Allocate XOL slots for uprobes use")
Cc: [email protected]
Acked-by: Masami Hiramatsu (Google) <[email protected]>
Signed-off-by: Oleg Nesterov <[email protected]>
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 2ec796e2f0553591c8a19a8512bf790686991c73..4b52cb2ae6d620b2526de7e86291bdc137aa4f49 100644 (file)
--- 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;