From 9380fa60b10ebd6ee7c3fcdb2cf162f4d7cf9fc5 Mon Sep 17 00:00:00 2001 From: Mateusz Jurczyk Date: Wed, 12 Jul 2017 14:34:01 -0700 Subject: [PATCH] kernel/sysctl_binary.c: check name array length in deprecated_sysctl_warning() Prevent use of uninitialized memory (originating from the stack frame of do_sysctl()) by verifying that the name array is filled with sufficient input data before comparing its specific entries with integer constants. Through timing measurement or analyzing the kernel debug logs, a user-mode program could potentially infer the results of comparisons against the uninitialized memory, and acquire some (very limited) information about the state of the kernel stack. The change also eliminates possible future warnings by tools such as KMSAN and other code checkers / instrumentations. Link: http://lkml.kernel.org/r/20170524122139.21333-1-mjurczyk@google.com Signed-off-by: Mateusz Jurczyk Acked-by: Kees Cook Cc: "David S. Miller" Cc: Matthew Whitehead Cc: "Eric W. Biederman" Cc: Tetsuo Handa Cc: Alexander Potapenko Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/sysctl_binary.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/sysctl_binary.c b/kernel/sysctl_binary.c index 939a158eab11..02e1859f2ca8 100644 --- a/kernel/sysctl_binary.c +++ b/kernel/sysctl_binary.c @@ -1346,7 +1346,7 @@ static void deprecated_sysctl_warning(const int *name, int nlen) * CTL_KERN/KERN_VERSION is used by older glibc and cannot * ever go away. */ - if (name[0] == CTL_KERN && name[1] == KERN_VERSION) + if (nlen >= 2 && name[0] == CTL_KERN && name[1] == KERN_VERSION) return; if (printk_ratelimit()) { -- 2.20.1