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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Jaakko Karrenpalo , Arvid Brodin , skhan@linuxfoundation.org, linux-kernel-mentees@lists.linux.dev, david.hunter.linux@gmail.com, khalid@kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+2fa344348a579b779e05@syzkaller.appspotmail.com, stable@vger.kernel.org Subject: Re: [PATCH net v3] net/hsr: fix NULL pointer dereference in prp_get_untagged_frame() Message-ID: References: <20251129093718.25320-1-ssrane_b23@ee.vjti.ac.in> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251129093718.25320-1-ssrane_b23@ee.vjti.ac.in> X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 On Sat, Nov 29, 2025 at 03:07:18PM +0530, Shaurya Rane wrote: > prp_get_untagged_frame() calls __pskb_copy() to create frame->skb_std > but doesn't check if the allocation failed. If __pskb_copy() returns > NULL, skb_clone() is called with a NULL pointer, causing a crash: > Oops: general protection fault, probably for non-canonical address 0xdffffc000000000f: 0000 [#1] SMP KASAN NOPTI > KASAN: null-ptr-deref in range [0x0000000000000078-0x000000000000007f] > CPU: 0 UID: 0 PID: 5625 Comm: syz.1.18 Not tainted syzkaller #0 PREEMPT(full) > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 > RIP: 0010:skb_clone+0xd7/0x3a0 net/core/skbuff.c:2041 > Code: 03 42 80 3c 20 00 74 08 4c 89 f7 e8 23 29 05 f9 49 83 3e 00 0f 85 a0 01 00 00 e8 94 dd 9d f8 48 8d 6b 7e 49 89 ee 49 c1 ee 03 <43> 0f b6 04 26 84 c0 0f 85 d1 01 00 00 44 0f b6 7d 00 41 83 e7 0c > RSP: 0018:ffffc9000d00f200 EFLAGS: 00010207 > RAX: ffffffff892235a1 RBX: 0000000000000000 RCX: ffff88803372a480 > RDX: 0000000000000000 RSI: 0000000000000820 RDI: 0000000000000000 > RBP: 000000000000007e R08: ffffffff8f7d0f77 R09: 1ffffffff1efa1ee > R10: dffffc0000000000 R11: fffffbfff1efa1ef R12: dffffc0000000000 > R13: 0000000000000820 R14: 000000000000000f R15: ffff88805144cc00 > FS: 0000555557f6d500(0000) GS:ffff88808d72f000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000555581d35808 CR3: 000000005040e000 CR4: 0000000000352ef0 > Call Trace: > > hsr_forward_do net/hsr/hsr_forward.c:-1 [inline] > hsr_forward_skb+0x1013/0x2860 net/hsr/hsr_forward.c:741 > hsr_handle_frame+0x6ce/0xa70 net/hsr/hsr_slave.c:84 > __netif_receive_skb_core+0x10b9/0x4380 net/core/dev.c:5966 > __netif_receive_skb_one_core net/core/dev.c:6077 [inline] > __netif_receive_skb+0x72/0x380 net/core/dev.c:6192 > netif_receive_skb_internal net/core/dev.c:6278 [inline] > netif_receive_skb+0x1cb/0x790 net/core/dev.c:6337 > tun_rx_batched+0x1b9/0x730 drivers/net/tun.c:1485 > tun_get_user+0x2b65/0x3e90 drivers/net/tun.c:1953 > tun_chr_write_iter+0x113/0x200 drivers/net/tun.c:1999 > 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/0xfa0 arch/x86/entry/syscall_64.c:94 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > RIP: 0033:0x7f0449f8e1ff > Code: 89 54 24 18 48 89 74 24 10 89 7c 24 08 e8 f9 92 02 00 48 8b 54 24 18 48 8b 74 24 10 41 89 c0 8b 7c 24 08 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 31 44 89 c7 48 89 44 24 08 e8 4c 93 02 00 48 > RSP: 002b:00007ffd7ad94c90 EFLAGS: 00000293 ORIG_RAX: 0000000000000001 > RAX: ffffffffffffffda RBX: 00007f044a1e5fa0 RCX: 00007f0449f8e1ff > RDX: 000000000000003e RSI: 0000200000000500 RDI: 00000000000000c8 > RBP: 00007ffd7ad94d20 R08: 0000000000000000 R09: 0000000000000000 > R10: 000000000000003e R11: 0000000000000293 R12: 0000000000000001 > R13: 00007f044a1e5fa0 R14: 00007f044a1e5fa0 R15: 0000000000000003 > > Add a NULL check immediately after __pskb_copy() to handle allocation > failures gracefully. Thank you, the fix looks good to me. Just a small nit pick (this can probably be done when applying): please add the empty lines around the trace again. Other than that: Reviewed-by: Felix Maurer Tested-by: Felix Maurer > Reported-by: syzbot+2fa344348a579b779e05@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=2fa344348a579b779e05 > Fixes: f266a683a480 ("net/hsr: Better frame dispatch") > Cc: stable@vger.kernel.org > Signed-off-by: Shaurya Rane > --- > v3: > - Keep only prp_get_untagged_frame() fix as the other two > NETIF_F_HW_HSR_TAG_INS checks are not needed for this bug > - Move NULL check immediately after __pskb_copy() call > > v2: > - Add stack trace to commit message > - Target net tree with [PATCH net] > - Add Cc: stable@vger.kernel.org > --- > net/hsr/hsr_forward.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/net/hsr/hsr_forward.c b/net/hsr/hsr_forward.c > index 339f0d220212..aefc9b6936ba 100644 > --- a/net/hsr/hsr_forward.c > +++ b/net/hsr/hsr_forward.c > @@ -205,6 +205,8 @@ struct sk_buff *prp_get_untagged_frame(struct hsr_frame_info *frame, > __pskb_copy(frame->skb_prp, > skb_headroom(frame->skb_prp), > GFP_ATOMIC); > + if (!frame->skb_std) > + return NULL; > } else { > /* Unexpected */ > WARN_ONCE(1, "%s:%d: Unexpected frame received (port_src %s)\n", > -- > 2.34.1 >