futex: Ensure that futex address is aligned in handle_futex_death()

commit 5a07168d8d89b00fe1760120714378175b3ef992 upstream. The futex code requires that the user space addresses of futexes are 32bit aligned. sys_futex() checks this in futex_get_keys() but the robust list code has no alignment check in place. As a consequence the kernel crashes on architectures with strict alignment requirements in handle_futex_death() when trying to cmpxchg() on an unaligned futex address which was retrieved from the robust list. [ tglx: Rewrote changelog, proper sizeof() based alignement check and add comment ] Fixes: 0771dfe ("[PATCH] lightweight robust futexes: core") Signed-off-by: Chen Jie <[email protected]> Signed-off-by: Thomas Gleixner <[email protected]> Cc: <[email protected]> Cc: <[email protected]> Cc: <[email protected]> Cc: [email protected] Link: https://lkml.kernel.org/r/[email protected] Signed-off-by: Greg Kroah-Hartman <[email protected]>
joaomiguelsm · Apr 3, 2019 · 2f59c12 · 2f59c12
1 parent 8df0d57
commit 2f59c12
Showing 1 changed file with 4 additions and 0 deletions.
diff --git a/kernel/futex.c b/kernel/futex.c
@@ -3067,6 +3067,10 @@ int handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi)
 {
 	u32 uval, uninitialized_var(nval), mval;
 
+	/* Futex address must be 32bit aligned */
+	if ((((unsigned long)uaddr) % sizeof(*uaddr)) != 0)
+		return -1;
+
 retry:
 	if (get_user(uval, uaddr))
 		return -1;