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Eric Dumazetdavem330
Eric Dumazet
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davem330
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tun: napi flags belong to tfile
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: 90e33d4 ("tun: enable napi_gro_frags() for TUN/TAP driver") Signed-off-by: Eric Dumazet <[email protected]> Reported-by: syzbot <[email protected]> Signed-off-by: David S. Miller <[email protected]>
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‎drivers/net/tun.c

Lines changed: 14 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -181,6 +181,7 @@ struct tun_file {
181181
};
182182
struct napi_struct napi;
183183
bool napi_enabled;
184+
bool napi_frags_enabled;
184185
struct mutex napi_mutex; /* Protects access to the above napi */
185186
struct list_head next;
186187
struct tun_struct *detached;
@@ -313,9 +314,10 @@ static int tun_napi_poll(struct napi_struct *napi, int budget)
313314
}
314315

315316
static void tun_napi_init(struct tun_struct *tun, struct tun_file *tfile,
316-
bool napi_en)
317+
bool napi_en, bool napi_frags)
317318
{
318319
tfile->napi_enabled = napi_en;
320+
tfile->napi_frags_enabled = napi_en && napi_frags;
319321
if (napi_en) {
320322
netif_napi_add(tun->dev, &tfile->napi, tun_napi_poll,
321323
NAPI_POLL_WEIGHT);
@@ -335,9 +337,9 @@ static void tun_napi_del(struct tun_file *tfile)
335337
netif_napi_del(&tfile->napi);
336338
}
337339

338-
static bool tun_napi_frags_enabled(const struct tun_struct *tun)
340+
static bool tun_napi_frags_enabled(const struct tun_file *tfile)
339341
{
340-
return READ_ONCE(tun->flags) & IFF_NAPI_FRAGS;
342+
return tfile->napi_frags_enabled;
341343
}
342344

343345
#ifdef CONFIG_TUN_VNET_CROSS_LE
@@ -792,7 +794,7 @@ static void tun_detach_all(struct net_device *dev)
792794
}
793795

794796
static int tun_attach(struct tun_struct *tun, struct file *file,
795-
bool skip_filter, bool napi)
797+
bool skip_filter, bool napi, bool napi_frags)
796798
{
797799
struct tun_file *tfile = file->private_data;
798800
struct net_device *dev = tun->dev;
@@ -865,7 +867,7 @@ static int tun_attach(struct tun_struct *tun, struct file *file,
865867
tun_enable_queue(tfile);
866868
} else {
867869
sock_hold(&tfile->sk);
868-
tun_napi_init(tun, tfile, napi);
870+
tun_napi_init(tun, tfile, napi, napi_frags);
869871
}
870872

871873
tun_set_real_num_queues(tun);
@@ -1708,7 +1710,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
17081710
int err;
17091711
u32 rxhash = 0;
17101712
int skb_xdp = 1;
1711-
bool frags = tun_napi_frags_enabled(tun);
1713+
bool frags = tun_napi_frags_enabled(tfile);
17121714

17131715
if (!(tun->dev->flags & IFF_UP))
17141716
return -EIO;
@@ -2533,7 +2535,8 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
25332535
return err;
25342536

25352537
err = tun_attach(tun, file, ifr->ifr_flags & IFF_NOFILTER,
2536-
ifr->ifr_flags & IFF_NAPI);
2538+
ifr->ifr_flags & IFF_NAPI,
2539+
ifr->ifr_flags & IFF_NAPI_FRAGS);
25372540
if (err < 0)
25382541
return err;
25392542

@@ -2631,7 +2634,8 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
26312634
(ifr->ifr_flags & TUN_FEATURES);
26322635

26332636
INIT_LIST_HEAD(&tun->disabled);
2634-
err = tun_attach(tun, file, false, ifr->ifr_flags & IFF_NAPI);
2637+
err = tun_attach(tun, file, false, ifr->ifr_flags & IFF_NAPI,
2638+
ifr->ifr_flags & IFF_NAPI_FRAGS);
26352639
if (err < 0)
26362640
goto err_free_flow;
26372641

@@ -2780,7 +2784,8 @@ static int tun_set_queue(struct file *file, struct ifreq *ifr)
27802784
ret = security_tun_dev_attach_queue(tun->security);
27812785
if (ret < 0)
27822786
goto unlock;
2783-
ret = tun_attach(tun, file, false, tun->flags & IFF_NAPI);
2787+
ret = tun_attach(tun, file, false, tun->flags & IFF_NAPI,
2788+
tun->flags & IFF_NAPI_FRAGS);
27842789
} else if (ifr->ifr_flags & IFF_DETACH_QUEUE) {
27852790
tun = rtnl_dereference(tfile->tun);
27862791
if (!tun || !(tun->flags & IFF_MULTI_QUEUE) || tfile->detached)

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