From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 314F61EE02F; Tue, 30 Sep 2025 15:03:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759244624; cv=none; b=Vl/woG/kvijPN3VVu7gLbYfAlkmpIggCwsCK7UACYLX7V8hFqVJ4FQxQJHvA3LGJOpzeAD/4MyL06+M7jS81nNQbCDPWxsxXmp7qQJ0RZSAMHBAFiWsicSxu7AYEF5i78Ok4vr1IdLhDQruvScBL86ZNk0gSjXgiudROQBvuM2I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759244624; c=relaxed/simple; bh=rn5DSqe9TVMrErglLhBdGyEyiA1zCxc0vf/pg1Mqvlw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=duWVYDieJ5+WHjEVm14lQdV7WH0CfoqOs1OG5As9Opo8aiaBN/DMtRpN7T6p7kkboY0YnWrIlOxqxRfc28iq1Yn1fqcXtyFsXVC4m71BW1OG6sCsQuadhOd7bMTyAb0cZEzjby9ZNREly2XyFJVIZvBsPehQuzy+o4/L5Lt9wWI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=q+/J8cKg; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="q+/J8cKg" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5B8D3C4CEF0; Tue, 30 Sep 2025 15:03:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1759244623; bh=rn5DSqe9TVMrErglLhBdGyEyiA1zCxc0vf/pg1Mqvlw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=q+/J8cKgxS/ZRM+qDGdG4CVanNsHC3nhyPgaacSUVE6ZOqNO0K+ZQFT2jL3BXpz9F +dPylM3ZYtp+fcn9G7VhyWssvfLYU+GlvNMZrFiozvK2ep3oe+ET6G0ficMQGam3Fw rRszoZOQBdZyHQC5GlhJ26Gwqm4hZTtqoi3muDjY= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+64e24275ad95a915a313@syzkaller.appspotmail.com, Wang Liang , Willem de Bruijn , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.16 065/143] net: tun: Update napi->skb after XDP process Date: Tue, 30 Sep 2025 16:46:29 +0200 Message-ID: <20250930143833.826641745@linuxfoundation.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20250930143831.236060637@linuxfoundation.org> References: <20250930143831.236060637@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.16-stable review patch. If anyone has any objections, please let me know. ------------------ From: Wang Liang [ Upstream commit 1091860a16a86ccdd77c09f2b21a5f634f5ab9ec ] 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: 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 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 Reviewed-by: Willem de Bruijn Link: https://patch.msgid.link/20250917113919.3991267-1-wangliang74@huawei.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- drivers/net/tun.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/net/tun.c b/drivers/net/tun.c index f8c5e2fd04dfa..0fffa023cb736 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -1863,6 +1863,9 @@ 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(); -- 2.51.0