[PATCH AUTOSEL 4.9 16/87] fs/file.c: initialize init_files.resize_wait

Sasha Levin
2019-03-27T18:21:17Z

From: Shuriyc Chu <sureeju@gmail.com>

[ Upstream commit 5704a06810682683355624923547b41540e2801a ]

(Taken from https://bugzilla.kernel.org/show_bug.cgi?id=200647)

'get_unused_fd_flags' in kthread cause kernel crash. It works fine on
4.1, but causes crash after get 64 fds. It also cause crash on
ubuntu1404/1604/1804, centos7.5, and the crash messages are almost the
same.

The crash message on centos7.5 shows below:

start fd 61
start fd 62
start fd 63
BUG: unable to handle kernel NULL pointer dereference at (null)
IP: __wake_up_common+0x2e/0x90
PGD 0
Oops: 0000 [#1] SMP
Modules linked in: test(OE) xt_CHECKSUM iptable_mangle ipt_MASQUERADE nf_nat_masquerade_ipv4 iptable_nat nf_nat_ipv4 nf_nat nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack nf_conntrack ipt_REJECT nf_reject_ipv4 tun bridge stp llc ebtable_filter ebtables ip6table_filter ip6_tables iptable_filter devlink sunrpc kvm_intel kvm irqbypass crc32_pclmul ghash_clmulni_intel aesni_intel lrw gf128mul glue_helper ablk_helper cryptd sg ppdev pcspkr virtio_balloon parport_pc parport i2c_piix4 joydev ip_tables xfs libcrc32c sr_mod cdrom sd_mod crc_t10dif crct10dif_generic ata_generic pata_acpi virtio_scsi virtio_console virtio_net cirrus drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops ttm crct10dif_pclmul crct10dif_common crc32c_intel drm ata_piix serio_raw libata virtio_pci virtio_ring i2c_core
virtio floppy dm_mirror dm_region_hash dm_log dm_mod
CPU: 2 PID: 1820 Comm: test_fd Kdump: loaded Tainted: G OE ------------ 3.10.0-862.3.3.el7.x86_64 #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.10.2-0-g5f4c7b1-prebuilt.qemu-project.org 04/01/2014
task: ffff8e92b9431fa0 ti: ffff8e94247a0000 task.ti: ffff8e94247a0000
RIP: 0010:__wake_up_common+0x2e/0x90
RSP: 0018:ffff8e94247a2d18 EFLAGS: 00010086
RAX: 0000000000000000 RBX: ffffffff9d09daa0 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000003 RDI: ffffffff9d09daa0
RBP: ffff8e94247a2d50 R08: 0000000000000000 R09: ffff8e92b95dfda8
R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff9d09daa8
R13: 0000000000000003 R14: 0000000000000000 R15: 0000000000000003
FS: 0000000000000000(0000) GS:ffff8e9434e80000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000017c686000 CR4: 00000000000207e0
Call Trace:
__wake_up+0x39/0x50
expand_files+0x131/0x250
__alloc_fd+0x47/0x170
get_unused_fd_flags+0x30/0x40
test_fd+0x12a/0x1c0 [test]
kthread+0xd1/0xe0
ret_from_fork_nospec_begin+0x21/0x21
Code: 66 90 55 48 89 e5 41 57 41 89 f7 41 56 41 89 ce 41 55 41 54 49 89 fc 49 83 c4 08 53 48 83 ec 10 48 8b 47 08 89 55 cc 4c 89 45 d0 <48> 8b 08 49 39 c4 48 8d 78 e8 4c 8d 69 e8 75 08 eb 3b 4c 89 ef
RIP __wake_up_common+0x2e/0x90
RSP <ffff8e94247a2d18>
CR2: 0000000000000000

This issue exists since CentOS 7.5 3.10.0-862 and CentOS 7.4
(3.10.0-693.21.1 ) is ok. Root cause: the item 'resize_wait' is not
initialized before being used.

Reported-by: Richard Zhang <zhang.zijian@h3c.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/file.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/fs/file.c b/fs/file.c
index 69d6990e3021..09aac4d4729b 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -475,6 +475,7 @@ struct files_struct init_files = {
.full_fds_bits = init_files.full_fds_bits_init,
},
.file_lock = __SPIN_LOCK_UNLOCKED(init_files.file_lock),
+ .resize_wait = __WAIT_QUEUE_HEAD_INITIALIZER(init_files.resize_wait),
};

static unsigned int find_next_fd(struct fdtable *fdt, unsigned int start)
--
2.19.1