From 28dd29c06d0dede4b32b2c559cff21955a830928 Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Mon, 1 Jul 2019 16:01:46 +0200 Subject: [PATCH] fork: return proper negative error code Make sure to return a proper negative error code from copy_process() when anon_inode_getfile() fails with CLONE_PIDFD. Otherwise _do_fork() will not detect an error and get_task_pid() will operator on a nonsensical pointer: R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dbc2c R13: 00007ffc15fbb0ff R14: 00007ff07e47e9c0 R15: 0000000000000000 kasan: CONFIG_KASAN_INLINE enabled kasan: GPF could be caused by NULL-ptr deref or user memory access general protection fault: 0000 [#1] PREEMPT SMP KASAN CPU: 1 PID: 7990 Comm: syz-executor290 Not tainted 5.2.0-rc6+ #9 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:__read_once_size include/linux/compiler.h:194 [inline] RIP: 0010:get_task_pid+0xe1/0x210 kernel/pid.c:372 Code: 89 ff e8 62 27 5f 00 49 8b 07 44 89 f1 4c 8d bc c8 90 01 00 00 eb 0c e8 0d fe 25 00 49 81 c7 38 05 00 00 4c 89 f8 48 c1 e8 03 <80> 3c 18 00 74 08 4c 89 ff e8 31 27 5f 00 4d 8b 37 e8 f9 47 12 00 RSP: 0018:ffff88808a4a7d78 EFLAGS: 00010203 RAX: 00000000000000a7 RBX: dffffc0000000000 RCX: ffff888088180600 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 RBP: ffff88808a4a7d90 R08: ffffffff814fb3a8 R09: ffffed1015d66bf8 R10: ffffed1015d66bf8 R11: 1ffff11015d66bf7 R12: 0000000000041ffc R13: 1ffff11011494fbc R14: 0000000000000000 R15: 000000000000053d FS: 00007ff07e47e700(0000) GS:ffff8880aeb00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000004b5100 CR3: 0000000094df2000 CR4: 00000000001406e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: _do_fork+0x1b9/0x5f0 kernel/fork.c:2360 __do_sys_clone kernel/fork.c:2454 [inline] __se_sys_clone kernel/fork.c:2448 [inline] __x64_sys_clone+0xc1/0xd0 kernel/fork.c:2448 do_syscall_64+0xfe/0x140 arch/x86/entry/common.c:301 entry_SYSCALL_64_after_hwframe+0x49/0xbe Link: https://lore.kernel.org/lkml/000000000000e0dc0d058c9e7142@google.com Reported-and-tested-by: syzbot+002e636502bc4b64eb5c@syzkaller.appspotmail.com Fixes: 6fd2fe494b17 ("copy_process(): don't use ksys_close() on cleanups") Cc: Jann Horn Cc: Al Viro Signed-off-by: Christian Brauner --- kernel/fork.c | 1 + 1 file changed, 1 insertion(+) diff --git a/kernel/fork.c b/kernel/fork.c index 61667909ce83..fe83343da24b 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -2036,6 +2036,7 @@ static __latent_entropy struct task_struct *copy_process( O_RDWR | O_CLOEXEC); if (IS_ERR(pidfile)) { put_unused_fd(pidfd); + retval = PTR_ERR(pidfile); goto bad_fork_free_pid; } get_pid(pid); /* held by pidfile now */ -- 2.30.2