* [PATCH net] net: tun: Update napi->skb after XDP process
@ 2025-09-17 11:39 Wang Liang
2025-09-18 14:30 ` Willem de Bruijn
` (2 more replies)
0 siblings, 3 replies; 5+ messages in thread
From: Wang Liang @ 2025-09-17 11:39 UTC (permalink / raw)
To: willemdebruijn.kernel, jasowang, andrew+netdev, davem, edumazet,
kuba, pabeni, ast, daniel, hawk, john.fastabend, sdf, lorenzo,
toke
Cc: yuehaibing, zhangchangzhong, wangliang74, linux-kernel, netdev
The syzbot report a UAF issue:
BUG: KASAN: slab-use-after-free in skb_reset_mac_header include/linux/skbuff.h:3150 [inline]
BUG: KASAN: slab-use-after-free in napi_frags_skb net/core/gro.c:723 [inline]
BUG: KASAN: slab-use-after-free in napi_gro_frags+0x6e/0x1030 net/core/gro.c:758
Read of size 8 at addr ffff88802ef22c18 by task syz.0.17/6079
CPU: 0 UID: 0 PID: 6079 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full)
Call Trace:
<TASK>
dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:378 [inline]
print_report+0xca/0x240 mm/kasan/report.c:482
kasan_report+0x118/0x150 mm/kasan/report.c:595
skb_reset_mac_header include/linux/skbuff.h:3150 [inline]
napi_frags_skb net/core/gro.c:723 [inline]
napi_gro_frags+0x6e/0x1030 net/core/gro.c:758
tun_get_user+0x28cb/0x3e20 drivers/net/tun.c:1920
tun_chr_write_iter+0x113/0x200 drivers/net/tun.c:1996
new_sync_write fs/read_write.c:593 [inline]
vfs_write+0x5c9/0xb30 fs/read_write.c:686
ksys_write+0x145/0x250 fs/read_write.c:738
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
</TASK>
Allocated by task 6079:
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:68
unpoison_slab_object mm/kasan/common.c:330 [inline]
__kasan_mempool_unpoison_object+0xa0/0x170 mm/kasan/common.c:558
kasan_mempool_unpoison_object include/linux/kasan.h:388 [inline]
napi_skb_cache_get+0x37b/0x6d0 net/core/skbuff.c:295
__alloc_skb+0x11e/0x2d0 net/core/skbuff.c:657
napi_alloc_skb+0x84/0x7d0 net/core/skbuff.c:811
napi_get_frags+0x69/0x140 net/core/gro.c:673
tun_napi_alloc_frags drivers/net/tun.c:1404 [inline]
tun_get_user+0x77c/0x3e20 drivers/net/tun.c:1784
tun_chr_write_iter+0x113/0x200 drivers/net/tun.c:1996
new_sync_write fs/read_write.c:593 [inline]
vfs_write+0x5c9/0xb30 fs/read_write.c:686
ksys_write+0x145/0x250 fs/read_write.c:738
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Freed by task 6079:
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:68
kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:576
poison_slab_object mm/kasan/common.c:243 [inline]
__kasan_slab_free+0x5b/0x80 mm/kasan/common.c:275
kasan_slab_free include/linux/kasan.h:233 [inline]
slab_free_hook mm/slub.c:2422 [inline]
slab_free mm/slub.c:4695 [inline]
kmem_cache_free+0x18f/0x400 mm/slub.c:4797
skb_pp_cow_data+0xdd8/0x13e0 net/core/skbuff.c:969
netif_skb_check_for_xdp net/core/dev.c:5390 [inline]
netif_receive_generic_xdp net/core/dev.c:5431 [inline]
do_xdp_generic+0x699/0x11a0 net/core/dev.c:5499
tun_get_user+0x2523/0x3e20 drivers/net/tun.c:1872
tun_chr_write_iter+0x113/0x200 drivers/net/tun.c:1996
new_sync_write fs/read_write.c:593 [inline]
vfs_write+0x5c9/0xb30 fs/read_write.c:686
ksys_write+0x145/0x250 fs/read_write.c:738
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
After commit e6d5dbdd20aa ("xdp: add multi-buff support for xdp running in
generic mode"), the original skb may be freed in skb_pp_cow_data() when
XDP program was attached, which was allocated in tun_napi_alloc_frags().
However, the napi->skb still point to the original skb, update it after
XDP process.
Reported-by: syzbot+64e24275ad95a915a313@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=64e24275ad95a915a313
Fixes: e6d5dbdd20aa ("xdp: add multi-buff support for xdp running in generic mode")
Signed-off-by: Wang Liang <wangliang74@huawei.com>
---
drivers/net/tun.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index cc6c50180663..47ddcb4b9a78 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1875,6 +1875,9 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
local_bh_enable();
goto unlock_frags;
}
+
+ if (frags && skb != tfile->napi.skb)
+ tfile->napi.skb = skb;
}
rcu_read_unlock();
local_bh_enable();
--
2.34.1
^ permalink raw reply related [flat|nested] 5+ messages in thread* Re: [PATCH net] net: tun: Update napi->skb after XDP process
2025-09-17 11:39 [PATCH net] net: tun: Update napi->skb after XDP process Wang Liang
@ 2025-09-18 14:30 ` Willem de Bruijn
2025-09-18 22:27 ` Willem de Bruijn
2025-09-19 14:46 ` Willem de Bruijn
2025-09-19 23:50 ` patchwork-bot+netdevbpf
2 siblings, 1 reply; 5+ messages in thread
From: Willem de Bruijn @ 2025-09-18 14:30 UTC (permalink / raw)
To: Wang Liang, willemdebruijn.kernel, jasowang, andrew+netdev, davem,
edumazet, kuba, pabeni, ast, daniel, hawk, john.fastabend, sdf,
lorenzo, toke
Cc: yuehaibing, zhangchangzhong, wangliang74, linux-kernel, netdev
Wang Liang wrote:
> The syzbot report a UAF issue:
>
> BUG: KASAN: slab-use-after-free in skb_reset_mac_header include/linux/skbuff.h:3150 [inline]
> BUG: KASAN: slab-use-after-free in napi_frags_skb net/core/gro.c:723 [inline]
> BUG: KASAN: slab-use-after-free in napi_gro_frags+0x6e/0x1030 net/core/gro.c:758
> Read of size 8 at addr ffff88802ef22c18 by task syz.0.17/6079
> CPU: 0 UID: 0 PID: 6079 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full)
> Call Trace:
> <TASK>
> dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
> print_address_description mm/kasan/report.c:378 [inline]
> print_report+0xca/0x240 mm/kasan/report.c:482
> kasan_report+0x118/0x150 mm/kasan/report.c:595
> skb_reset_mac_header include/linux/skbuff.h:3150 [inline]
> napi_frags_skb net/core/gro.c:723 [inline]
> napi_gro_frags+0x6e/0x1030 net/core/gro.c:758
> tun_get_user+0x28cb/0x3e20 drivers/net/tun.c:1920
> tun_chr_write_iter+0x113/0x200 drivers/net/tun.c:1996
> new_sync_write fs/read_write.c:593 [inline]
> vfs_write+0x5c9/0xb30 fs/read_write.c:686
> ksys_write+0x145/0x250 fs/read_write.c:738
> do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
> </TASK>
>
> Allocated by task 6079:
> kasan_save_stack mm/kasan/common.c:47 [inline]
> kasan_save_track+0x3e/0x80 mm/kasan/common.c:68
> unpoison_slab_object mm/kasan/common.c:330 [inline]
> __kasan_mempool_unpoison_object+0xa0/0x170 mm/kasan/common.c:558
> kasan_mempool_unpoison_object include/linux/kasan.h:388 [inline]
> napi_skb_cache_get+0x37b/0x6d0 net/core/skbuff.c:295
> __alloc_skb+0x11e/0x2d0 net/core/skbuff.c:657
> napi_alloc_skb+0x84/0x7d0 net/core/skbuff.c:811
> napi_get_frags+0x69/0x140 net/core/gro.c:673
> tun_napi_alloc_frags drivers/net/tun.c:1404 [inline]
> tun_get_user+0x77c/0x3e20 drivers/net/tun.c:1784
> tun_chr_write_iter+0x113/0x200 drivers/net/tun.c:1996
> new_sync_write fs/read_write.c:593 [inline]
> vfs_write+0x5c9/0xb30 fs/read_write.c:686
> ksys_write+0x145/0x250 fs/read_write.c:738
> do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
>
> Freed by task 6079:
> kasan_save_stack mm/kasan/common.c:47 [inline]
> kasan_save_track+0x3e/0x80 mm/kasan/common.c:68
> kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:576
> poison_slab_object mm/kasan/common.c:243 [inline]
> __kasan_slab_free+0x5b/0x80 mm/kasan/common.c:275
> kasan_slab_free include/linux/kasan.h:233 [inline]
> slab_free_hook mm/slub.c:2422 [inline]
> slab_free mm/slub.c:4695 [inline]
> kmem_cache_free+0x18f/0x400 mm/slub.c:4797
> skb_pp_cow_data+0xdd8/0x13e0 net/core/skbuff.c:969
> netif_skb_check_for_xdp net/core/dev.c:5390 [inline]
> netif_receive_generic_xdp net/core/dev.c:5431 [inline]
> do_xdp_generic+0x699/0x11a0 net/core/dev.c:5499
> tun_get_user+0x2523/0x3e20 drivers/net/tun.c:1872
> tun_chr_write_iter+0x113/0x200 drivers/net/tun.c:1996
> new_sync_write fs/read_write.c:593 [inline]
> vfs_write+0x5c9/0xb30 fs/read_write.c:686
> ksys_write+0x145/0x250 fs/read_write.c:738
> do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
>
> After commit e6d5dbdd20aa ("xdp: add multi-buff support for xdp running in
> generic mode"), the original skb may be freed in skb_pp_cow_data() when
> XDP program was attached, which was allocated in tun_napi_alloc_frags().
> However, the napi->skb still point to the original skb, update it after
> XDP process.
>
> Reported-by: syzbot+64e24275ad95a915a313@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=64e24275ad95a915a313
> Fixes: e6d5dbdd20aa ("xdp: add multi-buff support for xdp running in generic mode")
> Signed-off-by: Wang Liang <wangliang74@huawei.com>
> ---
> drivers/net/tun.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index cc6c50180663..47ddcb4b9a78 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -1875,6 +1875,9 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
> local_bh_enable();
> goto unlock_frags;
> }
> +
> + if (frags && skb != tfile->napi.skb)
> + tfile->napi.skb = skb;
This is observed with tun because syzkaller can fuzz napi with that.
That unfortunately added fuzz test coverage to a combination that is
not intended for real use: XDP generic before napi frags.
Tun is the only driver that calls do_xdp_generic on a napi.skb and
later passes this napi to napi_gro_frags.
But this is no longer a napi frags skb on which napi_gro_frags
(and napi_frags_skb and gro_pull_from_frag0) should be called? As the
skb now has a linear part. Not sure that the frag0 is still correct.
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH net] net: tun: Update napi->skb after XDP process
2025-09-18 14:30 ` Willem de Bruijn
@ 2025-09-18 22:27 ` Willem de Bruijn
0 siblings, 0 replies; 5+ messages in thread
From: Willem de Bruijn @ 2025-09-18 22:27 UTC (permalink / raw)
To: Willem de Bruijn, Wang Liang, willemdebruijn.kernel, jasowang,
andrew+netdev, davem, edumazet, kuba, pabeni, ast, daniel, hawk,
john.fastabend, sdf, lorenzo, toke
Cc: yuehaibing, zhangchangzhong, wangliang74, linux-kernel, netdev
Willem de Bruijn wrote:
> Wang Liang wrote:
> > The syzbot report a UAF issue:
> >
> > BUG: KASAN: slab-use-after-free in skb_reset_mac_header include/linux/skbuff.h:3150 [inline]
> > BUG: KASAN: slab-use-after-free in napi_frags_skb net/core/gro.c:723 [inline]
> > BUG: KASAN: slab-use-after-free in napi_gro_frags+0x6e/0x1030 net/core/gro.c:758
> > Read of size 8 at addr ffff88802ef22c18 by task syz.0.17/6079
> > CPU: 0 UID: 0 PID: 6079 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full)
> > Call Trace:
> > <TASK>
> > dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
> > print_address_description mm/kasan/report.c:378 [inline]
> > print_report+0xca/0x240 mm/kasan/report.c:482
> > kasan_report+0x118/0x150 mm/kasan/report.c:595
> > skb_reset_mac_header include/linux/skbuff.h:3150 [inline]
> > napi_frags_skb net/core/gro.c:723 [inline]
> > napi_gro_frags+0x6e/0x1030 net/core/gro.c:758
> > tun_get_user+0x28cb/0x3e20 drivers/net/tun.c:1920
> > tun_chr_write_iter+0x113/0x200 drivers/net/tun.c:1996
> > new_sync_write fs/read_write.c:593 [inline]
> > vfs_write+0x5c9/0xb30 fs/read_write.c:686
> > ksys_write+0x145/0x250 fs/read_write.c:738
> > do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> > do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
> > entry_SYSCALL_64_after_hwframe+0x77/0x7f
> > </TASK>
> >
> > Allocated by task 6079:
> > kasan_save_stack mm/kasan/common.c:47 [inline]
> > kasan_save_track+0x3e/0x80 mm/kasan/common.c:68
> > unpoison_slab_object mm/kasan/common.c:330 [inline]
> > __kasan_mempool_unpoison_object+0xa0/0x170 mm/kasan/common.c:558
> > kasan_mempool_unpoison_object include/linux/kasan.h:388 [inline]
> > napi_skb_cache_get+0x37b/0x6d0 net/core/skbuff.c:295
> > __alloc_skb+0x11e/0x2d0 net/core/skbuff.c:657
> > napi_alloc_skb+0x84/0x7d0 net/core/skbuff.c:811
> > napi_get_frags+0x69/0x140 net/core/gro.c:673
> > tun_napi_alloc_frags drivers/net/tun.c:1404 [inline]
> > tun_get_user+0x77c/0x3e20 drivers/net/tun.c:1784
> > tun_chr_write_iter+0x113/0x200 drivers/net/tun.c:1996
> > new_sync_write fs/read_write.c:593 [inline]
> > vfs_write+0x5c9/0xb30 fs/read_write.c:686
> > ksys_write+0x145/0x250 fs/read_write.c:738
> > do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> > do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
> > entry_SYSCALL_64_after_hwframe+0x77/0x7f
> >
> > Freed by task 6079:
> > kasan_save_stack mm/kasan/common.c:47 [inline]
> > kasan_save_track+0x3e/0x80 mm/kasan/common.c:68
> > kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:576
> > poison_slab_object mm/kasan/common.c:243 [inline]
> > __kasan_slab_free+0x5b/0x80 mm/kasan/common.c:275
> > kasan_slab_free include/linux/kasan.h:233 [inline]
> > slab_free_hook mm/slub.c:2422 [inline]
> > slab_free mm/slub.c:4695 [inline]
> > kmem_cache_free+0x18f/0x400 mm/slub.c:4797
> > skb_pp_cow_data+0xdd8/0x13e0 net/core/skbuff.c:969
> > netif_skb_check_for_xdp net/core/dev.c:5390 [inline]
> > netif_receive_generic_xdp net/core/dev.c:5431 [inline]
> > do_xdp_generic+0x699/0x11a0 net/core/dev.c:5499
> > tun_get_user+0x2523/0x3e20 drivers/net/tun.c:1872
> > tun_chr_write_iter+0x113/0x200 drivers/net/tun.c:1996
> > new_sync_write fs/read_write.c:593 [inline]
> > vfs_write+0x5c9/0xb30 fs/read_write.c:686
> > ksys_write+0x145/0x250 fs/read_write.c:738
> > do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> > do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
> > entry_SYSCALL_64_after_hwframe+0x77/0x7f
> >
> > After commit e6d5dbdd20aa ("xdp: add multi-buff support for xdp running in
> > generic mode"), the original skb may be freed in skb_pp_cow_data() when
> > XDP program was attached, which was allocated in tun_napi_alloc_frags().
> > However, the napi->skb still point to the original skb, update it after
> > XDP process.
> >
> > Reported-by: syzbot+64e24275ad95a915a313@syzkaller.appspotmail.com
> > Closes: https://syzkaller.appspot.com/bug?extid=64e24275ad95a915a313
> > Fixes: e6d5dbdd20aa ("xdp: add multi-buff support for xdp running in generic mode")
> > Signed-off-by: Wang Liang <wangliang74@huawei.com>
> > ---
> > drivers/net/tun.c | 3 +++
> > 1 file changed, 3 insertions(+)
> >
> > diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> > index cc6c50180663..47ddcb4b9a78 100644
> > --- a/drivers/net/tun.c
> > +++ b/drivers/net/tun.c
> > @@ -1875,6 +1875,9 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
> > local_bh_enable();
> > goto unlock_frags;
> > }
> > +
> > + if (frags && skb != tfile->napi.skb)
> > + tfile->napi.skb = skb;
>
> This is observed with tun because syzkaller can fuzz napi with that.
> That unfortunately added fuzz test coverage to a combination that is
> not intended for real use: XDP generic before napi frags.
>
> Tun is the only driver that calls do_xdp_generic on a napi.skb and
> later passes this napi to napi_gro_frags.
>
> But this is no longer a napi frags skb on which napi_gro_frags
> (and napi_frags_skb and gro_pull_from_frag0) should be called? As the
> skb now has a linear part. Not sure that the frag0 is still correct.
Never mind this. napi_alloc_skb may also fall back to a regular
__skb_alloc and pass that a napi.skb to napi_gro_frags. Which
reinitializes the NAPI_GRO_CB and with that frag0 accordingly.
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH net] net: tun: Update napi->skb after XDP process
2025-09-17 11:39 [PATCH net] net: tun: Update napi->skb after XDP process Wang Liang
2025-09-18 14:30 ` Willem de Bruijn
@ 2025-09-19 14:46 ` Willem de Bruijn
2025-09-19 23:50 ` patchwork-bot+netdevbpf
2 siblings, 0 replies; 5+ messages in thread
From: Willem de Bruijn @ 2025-09-19 14:46 UTC (permalink / raw)
To: Wang Liang, willemdebruijn.kernel, jasowang, andrew+netdev, davem,
edumazet, kuba, pabeni, ast, daniel, hawk, john.fastabend, sdf,
lorenzo, toke
Cc: yuehaibing, zhangchangzhong, wangliang74, linux-kernel, netdev
Wang Liang wrote:
> The syzbot report a UAF issue:
>
> BUG: KASAN: slab-use-after-free in skb_reset_mac_header include/linux/skbuff.h:3150 [inline]
> BUG: KASAN: slab-use-after-free in napi_frags_skb net/core/gro.c:723 [inline]
> BUG: KASAN: slab-use-after-free in napi_gro_frags+0x6e/0x1030 net/core/gro.c:758
> Read of size 8 at addr ffff88802ef22c18 by task syz.0.17/6079
> CPU: 0 UID: 0 PID: 6079 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full)
> Call Trace:
> <TASK>
> dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
> print_address_description mm/kasan/report.c:378 [inline]
> print_report+0xca/0x240 mm/kasan/report.c:482
> kasan_report+0x118/0x150 mm/kasan/report.c:595
> skb_reset_mac_header include/linux/skbuff.h:3150 [inline]
> napi_frags_skb net/core/gro.c:723 [inline]
> napi_gro_frags+0x6e/0x1030 net/core/gro.c:758
> tun_get_user+0x28cb/0x3e20 drivers/net/tun.c:1920
> tun_chr_write_iter+0x113/0x200 drivers/net/tun.c:1996
> new_sync_write fs/read_write.c:593 [inline]
> vfs_write+0x5c9/0xb30 fs/read_write.c:686
> ksys_write+0x145/0x250 fs/read_write.c:738
> do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
> </TASK>
>
> Allocated by task 6079:
> kasan_save_stack mm/kasan/common.c:47 [inline]
> kasan_save_track+0x3e/0x80 mm/kasan/common.c:68
> unpoison_slab_object mm/kasan/common.c:330 [inline]
> __kasan_mempool_unpoison_object+0xa0/0x170 mm/kasan/common.c:558
> kasan_mempool_unpoison_object include/linux/kasan.h:388 [inline]
> napi_skb_cache_get+0x37b/0x6d0 net/core/skbuff.c:295
> __alloc_skb+0x11e/0x2d0 net/core/skbuff.c:657
> napi_alloc_skb+0x84/0x7d0 net/core/skbuff.c:811
> napi_get_frags+0x69/0x140 net/core/gro.c:673
> tun_napi_alloc_frags drivers/net/tun.c:1404 [inline]
> tun_get_user+0x77c/0x3e20 drivers/net/tun.c:1784
> tun_chr_write_iter+0x113/0x200 drivers/net/tun.c:1996
> new_sync_write fs/read_write.c:593 [inline]
> vfs_write+0x5c9/0xb30 fs/read_write.c:686
> ksys_write+0x145/0x250 fs/read_write.c:738
> do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
>
> Freed by task 6079:
> kasan_save_stack mm/kasan/common.c:47 [inline]
> kasan_save_track+0x3e/0x80 mm/kasan/common.c:68
> kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:576
> poison_slab_object mm/kasan/common.c:243 [inline]
> __kasan_slab_free+0x5b/0x80 mm/kasan/common.c:275
> kasan_slab_free include/linux/kasan.h:233 [inline]
> slab_free_hook mm/slub.c:2422 [inline]
> slab_free mm/slub.c:4695 [inline]
> kmem_cache_free+0x18f/0x400 mm/slub.c:4797
> skb_pp_cow_data+0xdd8/0x13e0 net/core/skbuff.c:969
> netif_skb_check_for_xdp net/core/dev.c:5390 [inline]
> netif_receive_generic_xdp net/core/dev.c:5431 [inline]
> do_xdp_generic+0x699/0x11a0 net/core/dev.c:5499
> tun_get_user+0x2523/0x3e20 drivers/net/tun.c:1872
> tun_chr_write_iter+0x113/0x200 drivers/net/tun.c:1996
> new_sync_write fs/read_write.c:593 [inline]
> vfs_write+0x5c9/0xb30 fs/read_write.c:686
> ksys_write+0x145/0x250 fs/read_write.c:738
> do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
>
> After commit e6d5dbdd20aa ("xdp: add multi-buff support for xdp running in
> generic mode"), the original skb may be freed in skb_pp_cow_data() when
> XDP program was attached, which was allocated in tun_napi_alloc_frags().
> However, the napi->skb still point to the original skb, update it after
> XDP process.
>
> Reported-by: syzbot+64e24275ad95a915a313@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=64e24275ad95a915a313
> Fixes: e6d5dbdd20aa ("xdp: add multi-buff support for xdp running in generic mode")
> Signed-off-by: Wang Liang <wangliang74@huawei.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH net] net: tun: Update napi->skb after XDP process
2025-09-17 11:39 [PATCH net] net: tun: Update napi->skb after XDP process Wang Liang
2025-09-18 14:30 ` Willem de Bruijn
2025-09-19 14:46 ` Willem de Bruijn
@ 2025-09-19 23:50 ` patchwork-bot+netdevbpf
2 siblings, 0 replies; 5+ messages in thread
From: patchwork-bot+netdevbpf @ 2025-09-19 23:50 UTC (permalink / raw)
To: Wang Liang
Cc: willemdebruijn.kernel, jasowang, andrew+netdev, davem, edumazet,
kuba, pabeni, ast, daniel, hawk, john.fastabend, sdf, lorenzo,
toke, yuehaibing, zhangchangzhong, linux-kernel, netdev
Hello:
This patch was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:
On Wed, 17 Sep 2025 19:39:19 +0800 you wrote:
> The syzbot report a UAF issue:
>
> BUG: KASAN: slab-use-after-free in skb_reset_mac_header include/linux/skbuff.h:3150 [inline]
> BUG: KASAN: slab-use-after-free in napi_frags_skb net/core/gro.c:723 [inline]
> BUG: KASAN: slab-use-after-free in napi_gro_frags+0x6e/0x1030 net/core/gro.c:758
> Read of size 8 at addr ffff88802ef22c18 by task syz.0.17/6079
> CPU: 0 UID: 0 PID: 6079 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full)
> Call Trace:
> <TASK>
> dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
> print_address_description mm/kasan/report.c:378 [inline]
> print_report+0xca/0x240 mm/kasan/report.c:482
> kasan_report+0x118/0x150 mm/kasan/report.c:595
> skb_reset_mac_header include/linux/skbuff.h:3150 [inline]
> napi_frags_skb net/core/gro.c:723 [inline]
> napi_gro_frags+0x6e/0x1030 net/core/gro.c:758
> tun_get_user+0x28cb/0x3e20 drivers/net/tun.c:1920
> tun_chr_write_iter+0x113/0x200 drivers/net/tun.c:1996
> new_sync_write fs/read_write.c:593 [inline]
> vfs_write+0x5c9/0xb30 fs/read_write.c:686
> ksys_write+0x145/0x250 fs/read_write.c:738
> do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
> </TASK>
>
> [...]
Here is the summary with links:
- [net] net: tun: Update napi->skb after XDP process
https://git.kernel.org/netdev/net/c/1091860a16a8
You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2025-09-19 23:50 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2025-09-17 11:39 [PATCH net] net: tun: Update napi->skb after XDP process Wang Liang
2025-09-18 14:30 ` Willem de Bruijn
2025-09-18 22:27 ` Willem de Bruijn
2025-09-19 14:46 ` Willem de Bruijn
2025-09-19 23:50 ` patchwork-bot+netdevbpf
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