From 615c999cd8a07b7c3c93bbdee89ef705d2ce52e1 Mon Sep 17 00:00:00 2001 From: Manfred Spraul Date: Tue, 21 Aug 2018 22:01:21 -0700 Subject: ipc: compute kern_ipc_perm.id under the ipc lock ipc_addid() initializes kern_ipc_perm.id after having called ipc_idr_alloc(). Thus a parallel semctl() or msgctl() that uses e.g. MSG_STAT may use this unitialized value as the return code. The patch moves all accesses to kern_ipc_perm.id under the spin_lock(). The issues is related to the finding of syzbot+2827ef6b3385deb07eaf@syzkaller.appspotmail.com: syzbot found an issue with kern_ipc_perm.seq Link: http://lkml.kernel.org/r/20180712185241.4017-2-manfred@colorfullife.com Signed-off-by: Manfred Spraul Reviewed-by: Davidlohr Bueso Cc: Dmitry Vyukov Cc: Kees Cook Cc: Davidlohr Bueso Cc: Herbert Xu Cc: Michael Kerrisk Cc: Michal Hocko Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- ipc/sem.c | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-) (limited to 'ipc/sem.c') diff --git a/ipc/sem.c b/ipc/sem.c index 00ef2f743a62..18e50f464f76 100644 --- a/ipc/sem.c +++ b/ipc/sem.c @@ -1223,7 +1223,6 @@ static int semctl_stat(struct ipc_namespace *ns, int semid, { struct sem_array *sma; time64_t semotime; - int id = 0; int err; memset(semid64, 0, sizeof(*semid64)); @@ -1235,7 +1234,6 @@ static int semctl_stat(struct ipc_namespace *ns, int semid, err = PTR_ERR(sma); goto out_unlock; } - id = sma->sem_perm.id; } else { /* IPC_STAT */ sma = sem_obtain_object_check(ns, semid); if (IS_ERR(sma)) { @@ -1275,10 +1273,20 @@ static int semctl_stat(struct ipc_namespace *ns, int semid, #endif semid64->sem_nsems = sma->sem_nsems; + if (cmd == IPC_STAT) { + /* + * As defined in SUS: + * Return 0 on success + */ + err = 0; + } else { + /* + * SEM_STAT and SEM_STAT_ANY (both Linux specific) + * Return the full id, including the sequence number + */ + err = sma->sem_perm.id; + } ipc_unlock_object(&sma->sem_perm); - rcu_read_unlock(); - return id; - out_unlock: rcu_read_unlock(); return err; -- cgit v1.2.3-59-g8ed1b