From: Lu Shuaibing <shuaibinglu@xxxxxxx> commit 889b331724c82c11e15ba0a60979cf7bded0a26c upstream. A use of uninitialized memory in msgctl_down() because msqid64 in ksys_msgctl hasn't been initialized. The local | msqid64 | is created in ksys_msgctl() and then passed into msgctl_down(). Along the way msqid64 is never initialized before msgctl_down() checks msqid64->msg_qbytes. KUMSAN(KernelUninitializedMemorySantizer, a new error detection tool) reports: ================================================================== BUG: KUMSAN: use of uninitialized memory in msgctl_down+0x94/0x300 Read of size 8 at addr ffff88806bb97eb8 by task syz-executor707/2022 CPU: 0 PID: 2022 Comm: syz-executor707 Not tainted 5.2.0-rc4+ #63 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014 Call Trace: dump_stack+0x75/0xae __kumsan_report+0x17c/0x3e6 kumsan_report+0xe/0x20 msgctl_down+0x94/0x300 ksys_msgctl.constprop.14+0xef/0x260 do_syscall_64+0x7e/0x1f0 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x4400e9 Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 fb 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007ffd869e0598 EFLAGS: 00000246 ORIG_RAX: 0000000000000047 RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 00000000004400e9 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 RBP: 00000000006ca018 R08: 0000000000000000 R09: 0000000000000000 R10: 00000000ffffffff R11: 0000000000000246 R12: 0000000000401970 R13: 0000000000401a00 R14: 0000000000000000 R15: 0000000000000000 The buggy address belongs to the page: page:ffffea0001aee5c0 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 flags: 0x100000000000000() raw: 0100000000000000 0000000000000000 ffffffff01ae0101 0000000000000000 raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000 page dumped because: kumsan: bad access detected ================================================================== Syzkaller reproducer: msgctl$IPC_RMID(0x0, 0x0) C reproducer: // autogenerated by syzkaller (https://github.com/google/syzkaller) int main(void) { syscall(__NR_mmap, 0x20000000, 0x1000000, 3, 0x32, -1, 0); syscall(__NR_msgctl, 0, 0, 0); return 0; } [natechancellor@xxxxxxxxx: adjust indentation in ksys_msgctl] Link: https://github.com/ClangBuiltLinux/linux/issues/829 Link: http://lkml.kernel.org/r/20191218032932.37479-1-natechancellor@xxxxxxxxx Link: http://lkml.kernel.org/r/20190613014044.24234-1-shuaibinglu@xxxxxxx Signed-off-by: Lu Shuaibing <shuaibinglu@xxxxxxx> Signed-off-by: Nathan Chancellor <natechancellor@xxxxxxxxx> Suggested-by: Arnd Bergmann <arnd@xxxxxxxx> Cc: Davidlohr Bueso <dave@xxxxxxxxxxxx> Cc: Manfred Spraul <manfred@xxxxxxxxxxxxxxxx> Cc: NeilBrown <neilb@xxxxxxxx> From: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Subject: [PATCH 4.19 028/195] ipc/msg.c: consolidate all xxxctl_down() functions Each line here overflows 80 cols by exactly one character. Delete one tab per line to fix. Cc: Shaohua Li <shli@xxxxxx> Cc: Jens Axboe <axboe@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- ipc/msg.c | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-) --- a/ipc/msg.c +++ b/ipc/msg.c @@ -377,7 +377,7 @@ copy_msqid_from_user(struct msqid64_ds * * NOTE: no locks must be held, the rwsem is taken inside this function. */ static int msgctl_down(struct ipc_namespace *ns, int msqid, int cmd, - struct msqid64_ds *msqid64) + struct ipc64_perm *perm, int msg_qbytes) { struct kern_ipc_perm *ipcp; struct msg_queue *msq; @@ -387,7 +387,7 @@ static int msgctl_down(struct ipc_namesp rcu_read_lock(); ipcp = ipcctl_obtain_check(ns, &msg_ids(ns), msqid, cmd, - &msqid64->msg_perm, msqid64->msg_qbytes); + perm, msg_qbytes); if (IS_ERR(ipcp)) { err = PTR_ERR(ipcp); goto out_unlock1; @@ -409,18 +409,18 @@ static int msgctl_down(struct ipc_namesp { DEFINE_WAKE_Q(wake_q); - if (msqid64->msg_qbytes > ns->msg_ctlmnb && + if (msg_qbytes > ns->msg_ctlmnb && !capable(CAP_SYS_RESOURCE)) { err = -EPERM; goto out_unlock1; } ipc_lock_object(&msq->q_perm); - err = ipc_update_perm(&msqid64->msg_perm, ipcp); + err = ipc_update_perm(perm, ipcp); if (err) goto out_unlock0; - msq->q_qbytes = msqid64->msg_qbytes; + msq->q_qbytes = msg_qbytes; msq->q_ctime = ktime_get_real_seconds(); /* @@ -603,9 +603,10 @@ long ksys_msgctl(int msqid, int cmd, str case IPC_SET: if (copy_msqid_from_user(&msqid64, buf, version)) return -EFAULT; - /* fallthru */ + return msgctl_down(ns, msqid, cmd, &msqid64.msg_perm, + msqid64.msg_qbytes); case IPC_RMID: - return msgctl_down(ns, msqid, cmd, &msqid64); + return msgctl_down(ns, msqid, cmd, NULL, 0); default: return -EINVAL; } @@ -724,9 +725,9 @@ long compat_ksys_msgctl(int msqid, int c case IPC_SET: if (copy_compat_msqid_from_user(&msqid64, uptr, version)) return -EFAULT; - /* fallthru */ + return msgctl_down(ns, msqid, cmd, &msqid64.msg_perm, msqid64.msg_qbytes); case IPC_RMID: - return msgctl_down(ns, msqid, cmd, &msqid64); + return msgctl_down(ns, msqid, cmd, NULL, 0); default: return -EINVAL; }
