From: Mateusz Jurczyk <mjurczyk@xxxxxxxxxx> Subject: 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@xxxxxxxxxx Signed-off-by: Mateusz Jurczyk <mjurczyk@xxxxxxxxxx> Acked-by: Kees Cook <keescook@xxxxxxxxxxxx> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx> Cc: Matthew Whitehead <tedheadster@xxxxxxxxx> Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx> Cc: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> Cc: Alexander Potapenko <glider@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- kernel/sysctl_binary.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff -puN kernel/sysctl_binary.c~sysctl-check-name-array-length-in-deprecated_sysctl_warning kernel/sysctl_binary.c --- a/kernel/sysctl_binary.c~sysctl-check-name-array-length-in-deprecated_sysctl_warning +++ a/kernel/sysctl_binary.c @@ -1346,7 +1346,7 @@ static void deprecated_sysctl_warning(co * 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()) { _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
