[PATCH 4.18 032/135] tun: napi flags belong to tfile

Greg Kroah-Hartman
2018-10-16T17:11:40Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit af3fb24eecb2c59246e03c99386037fd5ad84ffd ]

Since tun->flags might be shared by multiple tfile structures,
it is better to make sure tun_get_user() is using the flags
for the current tfile.

Presence of the READ_ONCE() in tun_napi_frags_enabled() gave a hint
of what could happen, but we need something stronger to please
syzbot.

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: 0 PID: 13647 Comm: syz-executor5 Not tainted 4.19.0-rc5+ #59
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:dev_gro_receive+0x132/0x2720 net/core/dev.c:5427
Code: 48 c1 ea 03 80 3c 02 00 0f 85 6e 20 00 00 48 b8 00 00 00 00 00 fc ff df 4d 8b 6e 10 49 8d bd d0 00 00 00 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 59 20 00 00 4d 8b a5 d0 00 00 00 31 ff 41 81 e4
RSP: 0018:ffff8801c400f410 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff8618d325
RDX: 000000000000001a RSI: ffffffff86189f97 RDI: 00000000000000d0
RBP: ffff8801c400f608 R08: ffff8801c8fb4300 R09: 0000000000000000
R10: ffffed0038801ed7 R11: 0000000000000003 R12: ffff8801d327d358
R13: 0000000000000000 R14: ffff8801c16dd8c0 R15: 0000000000000004
FS: 00007fe003615700(0000) GS:ffff8801dac00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fe1f3c43db8 CR3: 00000001bebb2000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
napi_gro_frags+0x3f4/0xc90 net/core/dev.c:5715
tun_get_user+0x31d5/0x42a0 drivers/net/tun.c:1922
tun_chr_write_iter+0xb9/0x154 drivers/net/tun.c:1967
call_write_iter include/linux/fs.h:1808 [inline]
new_sync_write fs/read_write.c:474 [inline]
__vfs_write+0x6b8/0x9f0 fs/read_write.c:487
vfs_write+0x1fc/0x560 fs/read_write.c:549
ksys_write+0x101/0x260 fs/read_write.c:598
__do_sys_write fs/read_write.c:610 [inline]
__se_sys_write fs/read_write.c:607 [inline]
__x64_sys_write+0x73/0xb0 fs/read_write.c:607
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457579
Code: 1d b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 eb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fe003614c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000457579
RDX: 0000000000000012 RSI: 0000000020000000 RDI: 000000000000000a
RBP: 000000000072c040 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fe0036156d4
R13: 00000000004c5574 R14: 00000000004d8e98 R15: 00000000ffffffff
Modules linked in:

RIP: 0010:dev_gro_receive+0x132/0x2720 net/core/dev.c:5427
Code: 48 c1 ea 03 80 3c 02 00 0f 85 6e 20 00 00 48 b8 00 00 00 00 00 fc ff df 4d 8b 6e 10 49 8d bd d0 00 00 00 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 59 20 00 00 4d 8b a5 d0 00 00 00 31 ff 41 81 e4
RSP: 0018:ffff8801c400f410 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff8618d325
RDX: 000000000000001a RSI: ffffffff86189f97 RDI: 00000000000000d0
RBP: ffff8801c400f608 R08: ffff8801c8fb4300 R09: 0000000000000000
R10: ffffed0038801ed7 R11: 0000000000000003 R12: ffff8801d327d358
R13: 0000000000000000 R14: ffff8801c16dd8c0 R15: 0000000000000004
FS: 00007fe003615700(0000) GS:ffff8801dac00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fe1f3c43db8 CR3: 00000001bebb2000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

Fixes: 90e33d459407 ("tun: enable napi_gro_frags() for TUN/TAP driver")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/tun.c | 29 ++++++++++++++++-------------
1 file changed, 16 insertions(+), 13 deletions(-)

--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -181,6 +181,7 @@ struct tun_file {
};
struct napi_struct napi;
bool napi_enabled;
+ bool napi_frags_enabled;
struct mutex napi_mutex; /* Protects access to the above napi */
struct list_head next;
struct tun_struct *detached;
@@ -312,9 +313,10 @@ static int tun_napi_poll(struct napi_str
}

static void tun_napi_init(struct tun_struct *tun, struct tun_file *tfile,
- bool napi_en)
+ bool napi_en, bool napi_frags)
{
tfile->napi_enabled = napi_en;
+ tfile->napi_frags_enabled = napi_en && napi_frags;
if (napi_en) {
netif_napi_add(tun->dev, &tfile->napi, tun_napi_poll,
NAPI_POLL_WEIGHT);
@@ -334,9 +336,9 @@ static void tun_napi_del(struct tun_file
netif_napi_del(&tfile->napi);
}

-static bool tun_napi_frags_enabled(const struct tun_struct *tun)
+static bool tun_napi_frags_enabled(const struct tun_file *tfile)
{
- return READ_ONCE(tun->flags) & IFF_NAPI_FRAGS;
+ return tfile->napi_frags_enabled;
}

#ifdef CONFIG_TUN_VNET_CROSS_LE
@@ -790,7 +792,7 @@ static void tun_detach_all(struct net_de
}

static int tun_attach(struct tun_struct *tun, struct file *file,
- bool skip_filter, bool napi)
+ bool skip_filter, bool napi, bool napi_frags)
{
struct tun_file *tfile = file->private_data;
struct net_device *dev = tun->dev;
@@ -863,7 +865,7 @@ static int tun_attach(struct tun_struct
tun_enable_queue(tfile);
} else {
sock_hold(&tfile->sk);
- tun_napi_init(tun, tfile, napi);
+ tun_napi_init(tun, tfile, napi, napi_frags);
}

tun_set_real_num_queues(tun);
@@ -1173,13 +1175,11 @@ static void tun_poll_controller(struct n
struct tun_file *tfile;
int i;

- if (tun_napi_frags_enabled(tun))
- return;
-
rcu_read_lock();
for (i = 0; i < tun->numqueues; i++) {
tfile = rcu_dereference(tun->tfiles[i]);
- if (tfile->napi_enabled)
+ if (!tun_napi_frags_enabled(tfile) &&
+ tfile->napi_enabled)
napi_schedule(&tfile->napi);
}
rcu_read_unlock();
@@ -1750,7 +1750,7 @@ static ssize_t tun_get_user(struct tun_s
int err;
u32 rxhash = 0;
int skb_xdp = 1;
- bool frags = tun_napi_frags_enabled(tun);
+ bool frags = tun_napi_frags_enabled(tfile);

if (!(tun->dev->flags & IFF_UP))
return -EIO;
@@ -2575,7 +2575,8 @@ static int tun_set_iff(struct net *net,
return err;

err = tun_attach(tun, file, ifr->ifr_flags & IFF_NOFILTER,
- ifr->ifr_flags & IFF_NAPI);
+ ifr->ifr_flags & IFF_NAPI,
+ ifr->ifr_flags & IFF_NAPI_FRAGS);
if (err < 0)
return err;

@@ -2673,7 +2674,8 @@ static int tun_set_iff(struct net *net,
(ifr->ifr_flags & TUN_FEATURES);

INIT_LIST_HEAD(&tun->disabled);
- err = tun_attach(tun, file, false, ifr->ifr_flags & IFF_NAPI);
+ err = tun_attach(tun, file, false, ifr->ifr_flags & IFF_NAPI,
+ ifr->ifr_flags & IFF_NAPI_FRAGS);
if (err < 0)
goto err_free_flow;

@@ -2822,7 +2824,8 @@ static int tun_set_queue(struct file *fi
ret = security_tun_dev_attach_queue(tun->security);
if (ret < 0)
goto unlock;
- ret = tun_attach(tun, file, false, tun->flags & IFF_NAPI);
+ ret = tun_attach(tun, file, false, tun->flags & IFF_NAPI,
+ tun->flags & IFF_NAPI_FRAGS);
} else if (ifr->ifr_flags & IFF_DETACH_QUEUE) {
tun = rtnl_dereference(tfile->tun);
if (!tun || !(tun->flags & IFF_MULTI_QUEUE) || tfile->detached)