From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-180.mta0.migadu.com (out-180.mta0.migadu.com [91.218.175.180]) (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 14EC124B29 for ; Fri, 26 Jul 2024 19:11:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.180 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722021120; cv=none; b=EITxFwURc7Zv6Ylf3Lrld3bLVHev1dThGjPjSbXQWRQ8noc0E94dZnlfAgKAekm/Vg6fbIFASt/6kWWWz4WiSjNai/RAO1XRNiBxGfZM22jNerzEaMrh0TaTIsebCF9Abjsdk0mO+E9cBQC2UkkG9cHNzdAYvjA+uED+6Q8EBZo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722021120; c=relaxed/simple; bh=xsNcZpxhqz7lYTXv6JZF/aPuH5T3lM+z2ev2/BGePS0=; h=Message-ID:Date:MIME-Version:Subject:To:References:From: In-Reply-To:Content-Type; b=QX7WWzOuuegAZS3SkLYpPw/q60/rObEJpccgKU6CghAXaUgmJ13U5G7ySyHum/gOWQCAxzrtr+wNShK2lSb4L8urXp/dWDeu5FwKYulkZejHvmREBnp86AR2Wju8apN1BOctGn7wlTNbyqvasuzfP+GWnkKkbL35roRQVEU9uEs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=exCAoi3Q; arc=none smtp.client-ip=91.218.175.180 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="exCAoi3Q" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1722021115; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=FMe+NyN/q9/GuDK5HPMTsbfBCYT70sLw4NcA2oqRunA=; b=exCAoi3Q+kC0NxHWwr/+3mN33tjL60QD6H0+yXBVdD65c3QX4lKwsg9BFw13Excoaau9Bz 4BBY88UeF1l94wr7z+i1Qex/FrivGKBXV4AXkoJ1IPU0rsK4tHVa3Xkb3d6gi4v2Wa7cCT mbQpUS01s5FowWqwp5EZkc4yL+wv27k= Date: Fri, 26 Jul 2024 12:11:47 -0700 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH] bpf, cpumap: Fix use after free of bpf_cpu_map_entry in cpu_map_enqueue Content-Language: en-GB To: =?UTF-8?Q?Toke_H=C3=B8iland-J=C3=B8rgensen?= , Radoslaw Zielonek , ast@kernel.org, daniel@iogearbox.net, davem@davemloft.net, kuba@kernel.org, hawk@kernel.org, john.fastabend@gmail.com, andrii@kernel.org, martin.lau@linux.dev, eddyz87@gmail.com, song@kernel.org, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, jolsa@kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org References: <20240726180157.1065502-2-radoslaw.zielonek@gmail.com> <87h6ccnft1.fsf@toke.dk> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Yonghong Song In-Reply-To: <87h6ccnft1.fsf@toke.dk> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT On 7/26/24 11:55 AM, Toke Høiland-Jørgensen wrote: > Radoslaw Zielonek writes: > >> When cpu_map has been redirected, first the pointer to the >> bpf_cpu_map_entry has been copied, then freed, and read from the copy. >> To fix it, this commit introduced the refcount cpu_map_parent during >> redirections to prevent use after free. >> >> syzbot reported: >> >> [ 61.581464][T11670] ================================================================== >> [ 61.583323][T11670] BUG: KASAN: slab-use-after-free in cpu_map_enqueue+0xba/0x370 >> [ 61.585419][T11670] Read of size 8 at addr ffff888122d75208 by task syzbot-repro/11670 >> [ 61.587541][T11670] >> [ 61.588237][T11670] CPU: 1 PID: 11670 Comm: syzbot-repro Not tainted 6.9.0-rc6-00053-g0106679839f7 #27 >> [ 61.590542][T11670] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.1 11/11/2019 >> [ 61.592798][T11670] Call Trace: >> [ 61.593885][T11670] >> [ 61.594805][T11670] dump_stack_lvl+0x241/0x360 >> [ 61.595974][T11670] ? tcp_gro_dev_warn+0x260/0x260 >> [ 61.598242][T11670] ? __wake_up_klogd+0xcc/0x100 >> [ 61.599407][T11670] ? panic+0x850/0x850 >> [ 61.600516][T11670] ? __virt_addr_valid+0x182/0x510 >> [ 61.602073][T11670] ? __virt_addr_valid+0x182/0x510 >> [ 61.603496][T11670] print_address_description+0x7b/0x360 >> [ 61.605170][T11670] print_report+0xfd/0x210 >> [ 61.606370][T11670] ? __virt_addr_valid+0x182/0x510 >> [ 61.607925][T11670] ? __virt_addr_valid+0x182/0x510 >> [ 61.609577][T11670] ? __virt_addr_valid+0x43d/0x510 >> [ 61.610948][T11670] ? __phys_addr+0xb9/0x170 >> [ 61.612103][T11670] ? cpu_map_enqueue+0xba/0x370 >> [ 61.613448][T11670] kasan_report+0x143/0x180 >> [ 61.615000][T11670] ? cpu_map_enqueue+0xba/0x370 >> [ 61.616181][T11670] cpu_map_enqueue+0xba/0x370 >> [ 61.617620][T11670] xdp_do_redirect+0x685/0xbf0 >> [ 61.618787][T11670] tun_xdp_act+0xe7/0x9e0 >> [ 61.619856][T11670] ? __tun_build_skb+0x2e0/0x2e0 >> [ 61.621356][T11670] tun_build_skb+0xac6/0x1140 >> [ 61.622602][T11670] ? tun_build_skb+0xb4/0x1140 >> [ 61.623880][T11670] ? tun_get_user+0x2760/0x2760 >> [ 61.625341][T11670] tun_get_user+0x7fa/0x2760 >> [ 61.626532][T11670] ? rcu_read_unlock+0xa0/0xa0 >> [ 61.627725][T11670] ? tun_get+0x1e/0x2f0 >> [ 61.629147][T11670] ? tun_get+0x1e/0x2f0 >> [ 61.630265][T11670] ? tun_get+0x27d/0x2f0 >> [ 61.631486][T11670] tun_chr_write_iter+0x111/0x1f0 >> [ 61.632855][T11670] vfs_write+0xa84/0xcb0 >> [ 61.634185][T11670] ? __lock_acquire+0x1f60/0x1f60 >> [ 61.635501][T11670] ? kernel_write+0x330/0x330 >> [ 61.636757][T11670] ? lockdep_hardirqs_on_prepare+0x43c/0x780 >> [ 61.638445][T11670] ? __fget_files+0x3ea/0x460 >> [ 61.639448][T11670] ? seqcount_lockdep_reader_access+0x157/0x220 >> [ 61.641217][T11670] ? __fdget_pos+0x19e/0x320 >> [ 61.642426][T11670] ksys_write+0x19f/0x2c0 >> [ 61.643576][T11670] ? __ia32_sys_read+0x90/0x90 >> [ 61.644841][T11670] ? ktime_get_coarse_real_ts64+0x10b/0x120 >> [ 61.646549][T11670] do_syscall_64+0xec/0x210 >> [ 61.647832][T11670] entry_SYSCALL_64_after_hwframe+0x67/0x6f >> [ 61.649485][T11670] RIP: 0033:0x472a4f >> [ 61.650539][T11670] Code: 89 54 24 18 48 89 74 24 10 89 7c 24 08 e8 c9 d8 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 0c d9 02 00 48 >> [ 61.655476][T11670] RSP: 002b:00007f7a7a90f5c0 EFLAGS: 00000293 ORIG_RAX: 0000000000000001 >> [ 61.657675][T11670] RAX: ffffffffffffffda RBX: 00007f7a7a911640 RCX: 0000000000472a4f >> [ 61.659658][T11670] RDX: 0000000000000066 RSI: 0000000020000440 RDI: 00000000000000c8 >> [ 61.661980][T11670] RBP: 00007f7a7a90f620 R08: 0000000000000000 R09: 0000000100000000 >> [ 61.663982][T11670] R10: 0000000100000000 R11: 0000000000000293 R12: 00007f7a7a911640 >> [ 61.666425][T11670] R13: 000000000000006e R14: 000000000042f2f0 R15: 00007f7a7a8f1000 >> [ 61.668443][T11670] >> [ 61.669233][T11670] >> [ 61.669754][T11670] Allocated by task 11643: >> [ 61.670855][T11670] kasan_save_track+0x3f/0x70 >> [ 61.672094][T11670] __kasan_kmalloc+0x98/0xb0 >> [ 61.673466][T11670] __kmalloc_node+0x259/0x4f0 >> [ 61.674687][T11670] bpf_map_kmalloc_node+0xd3/0x1c0 >> [ 61.676069][T11670] cpu_map_update_elem+0x2f0/0x1000 >> [ 61.677619][T11670] bpf_map_update_value+0x1b2/0x540 >> [ 61.679006][T11670] map_update_elem+0x52f/0x6e0 >> [ 61.680076][T11670] __sys_bpf+0x7a9/0x850 >> [ 61.681610][T11670] __x64_sys_bpf+0x7c/0x90 >> [ 61.682772][T11670] do_syscall_64+0xec/0x210 >> [ 61.683967][T11670] entry_SYSCALL_64_after_hwframe+0x67/0x6f >> [ 61.685648][T11670] >> [ 61.686282][T11670] Freed by task 1064: >> [ 61.687296][T11670] kasan_save_track+0x3f/0x70 >> [ 61.688498][T11670] kasan_save_free_info+0x40/0x50 >> [ 61.689786][T11670] poison_slab_object+0xa6/0xe0 >> [ 61.691059][T11670] __kasan_slab_free+0x37/0x60 >> [ 61.692336][T11670] kfree+0x136/0x2f0 >> [ 61.693549][T11670] __cpu_map_entry_free+0x6f3/0x770 >> [ 61.695004][T11670] cpu_map_free+0xc0/0x180 >> [ 61.696191][T11670] bpf_map_free_deferred+0xe3/0x100 >> [ 61.697703][T11670] process_scheduled_works+0x9cb/0x14a0 >> [ 61.699330][T11670] worker_thread+0x85c/0xd50 >> [ 61.700546][T11670] kthread+0x2ef/0x390 >> [ 61.701791][T11670] ret_from_fork+0x4d/0x80 >> [ 61.702942][T11670] ret_from_fork_asm+0x11/0x20 >> [ 61.704195][T11670] >> [ 61.704825][T11670] The buggy address belongs to the object at ffff888122d75200 >> [ 61.704825][T11670] which belongs to the cache kmalloc-cg-256 of size 256 >> [ 61.708516][T11670] The buggy address is located 8 bytes inside of >> [ 61.708516][T11670] freed 256-byte region [ffff888122d75200, ffff888122d75300) >> [ 61.712215][T11670] >> [ 61.712824][T11670] The buggy address belongs to the physical page: >> [ 61.714883][T11670] page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x122d74 >> [ 61.717300][T11670] head: order:1 entire_mapcount:0 nr_pages_mapped:0 pincount:0 >> [ 61.719037][T11670] memcg:ffff888120d85f01 >> [ 61.720006][T11670] flags: 0x17ff00000000840(slab|head|node=0|zone=2|lastcpupid=0x7ff) >> [ 61.722181][T11670] page_type: 0xffffffff() >> [ 61.723318][T11670] raw: 017ff00000000840 ffff88810004dcc0 dead000000000122 0000000000000000 >> [ 61.725650][T11670] raw: 0000000000000000 0000000080100010 00000001ffffffff ffff888120d85f01 >> [ 61.727943][T11670] head: 017ff00000000840 ffff88810004dcc0 dead000000000122 0000000000000000 >> [ 61.730237][T11670] head: 0000000000000000 0000000080100010 00000001ffffffff ffff888120d85f01 >> [ 61.732671][T11670] head: 017ff00000000001 ffffea00048b5d01 dead000000000122 00000000ffffffff >> [ 61.735029][T11670] head: 0000000200000000 0000000000000000 00000000ffffffff 0000000000000000 >> [ 61.737400][T11670] page dumped because: kasan: bad access detected >> [ 61.740100][T11670] page_owner tracks the page as allocated >> [ 61.743121][T11670] page last allocated via order 1, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 8343, tgid -2092279795 (syzbot-repro), ts 8343, free_ts 43505720198 >> [ 61.754038][T11670] post_alloc_hook+0x1e6/0x210 >> [ 61.756046][T11670] get_page_from_freelist+0x7d2/0x850 >> [ 61.759460][T11670] __alloc_pages+0x25e/0x580 >> [ 61.761428][T11670] alloc_slab_page+0x6b/0x1a0 >> [ 61.764199][T11670] allocate_slab+0x5d/0x200 >> [ 61.766122][T11670] ___slab_alloc+0xac5/0xf20 >> [ 61.767195][T11670] __kmalloc+0x2e0/0x4b0 >> [ 61.769028][T11670] fib_default_rule_add+0x4a/0x350 >> [ 61.770394][T11670] fib6_rules_net_init+0x42/0x100 >> [ 61.771731][T11670] ops_init+0x39d/0x670 >> [ 61.773061][T11670] setup_net+0x3bc/0xae0 >> [ 61.774102][T11670] copy_net_ns+0x399/0x5e0 >> [ 61.775628][T11670] create_new_namespaces+0x4de/0x8d0 >> [ 61.776950][T11670] unshare_nsproxy_namespaces+0x127/0x190 >> [ 61.778352][T11670] ksys_unshare+0x5e6/0xbf0 >> [ 61.779741][T11670] __x64_sys_unshare+0x38/0x40 >> [ 61.781302][T11670] page last free pid 4619 tgid 4619 stack trace: >> [ 61.783542][T11670] free_unref_page_prepare+0x72f/0x7c0 >> [ 61.785018][T11670] free_unref_page+0x37/0x3f0 >> [ 61.786030][T11670] __slab_free+0x351/0x3f0 >> [ 61.786991][T11670] qlist_free_all+0x60/0xd0 >> [ 61.788827][T11670] kasan_quarantine_reduce+0x15a/0x170 >> [ 61.789951][T11670] __kasan_slab_alloc+0x23/0x70 >> [ 61.790999][T11670] kmem_cache_alloc_node+0x193/0x390 >> [ 61.792331][T11670] kmalloc_reserve+0xa7/0x2a0 >> [ 61.793345][T11670] __alloc_skb+0x1ec/0x430 >> [ 61.794435][T11670] netlink_sendmsg+0x615/0xc80 >> [ 61.796439][T11670] __sock_sendmsg+0x21f/0x270 >> [ 61.797467][T11670] ____sys_sendmsg+0x540/0x860 >> [ 61.798505][T11670] __sys_sendmsg+0x2b7/0x3a0 >> [ 61.799512][T11670] do_syscall_64+0xec/0x210 >> [ 61.800674][T11670] entry_SYSCALL_64_after_hwframe+0x67/0x6f >> [ 61.802021][T11670] >> [ 61.802526][T11670] Memory state around the buggy address: >> [ 61.803701][T11670] ffff888122d75100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >> [ 61.805694][T11670] ffff888122d75180: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >> [ 61.808104][T11670] >ffff888122d75200: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >> [ 61.809769][T11670] ^ >> [ 61.810672][T11670] ffff888122d75280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >> [ 61.812532][T11670] ffff888122d75300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >> [ 61.814846][T11670] ================================================================== >> [ 61.816914][T11670] Kernel panic - not syncing: KASAN: panic_on_warn set ... >> [ 61.818415][T11670] CPU: 1 PID: 11670 Comm: syzbot-repro Not tainted 6.9.0-rc6-00053-g0106679839f7 #27 >> [ 61.821191][T11670] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.1 11/11/2019 >> [ 61.822911][T11670] Call Trace: >> [ 61.823632][T11670] >> [ 61.824525][T11670] dump_stack_lvl+0x241/0x360 >> [ 61.825545][T11670] ? tcp_gro_dev_warn+0x260/0x260 >> [ 61.826706][T11670] ? panic+0x850/0x850 >> [ 61.828594][T11670] ? lock_release+0x85/0x860 >> [ 61.829749][T11670] ? vscnprintf+0x5d/0x80 >> [ 61.830951][T11670] panic+0x335/0x850 >> [ 61.832316][T11670] ? check_panic_on_warn+0x21/0xa0 >> [ 61.834475][T11670] ? __memcpy_flushcache+0x2c0/0x2c0 >> [ 61.835809][T11670] ? _raw_spin_unlock_irqrestore+0xd8/0x140 >> [ 61.838063][T11670] ? _raw_spin_unlock_irqrestore+0xdd/0x140 >> [ 61.842056][T11670] ? _raw_spin_unlock+0x40/0x40 >> [ 61.843116][T11670] ? print_report+0x1cc/0x210 >> [ 61.844527][T11670] check_panic_on_warn+0x82/0xa0 >> [ 61.845336][T11670] ? cpu_map_enqueue+0xba/0x370 >> [ 61.846117][T11670] end_report+0x48/0xa0 >> [ 61.846790][T11670] kasan_report+0x154/0x180 >> [ 61.847520][T11670] ? cpu_map_enqueue+0xba/0x370 >> [ 61.848471][T11670] cpu_map_enqueue+0xba/0x370 >> [ 61.849968][T11670] xdp_do_redirect+0x685/0xbf0 >> [ 61.850994][T11670] tun_xdp_act+0xe7/0x9e0 >> [ 61.851703][T11670] ? __tun_build_skb+0x2e0/0x2e0 >> [ 61.852598][T11670] tun_build_skb+0xac6/0x1140 >> [ 61.853362][T11670] ? tun_build_skb+0xb4/0x1140 >> [ 61.854454][T11670] ? tun_get_user+0x2760/0x2760 >> [ 61.855806][T11670] tun_get_user+0x7fa/0x2760 >> [ 61.856734][T11670] ? rcu_read_unlock+0xa0/0xa0 >> [ 61.857502][T11670] ? tun_get+0x1e/0x2f0 >> [ 61.858171][T11670] ? tun_get+0x1e/0x2f0 >> [ 61.858952][T11670] ? tun_get+0x27d/0x2f0 >> [ 61.859637][T11670] tun_chr_write_iter+0x111/0x1f0 >> [ 61.860913][T11670] vfs_write+0xa84/0xcb0 >> [ 61.861578][T11670] ? __lock_acquire+0x1f60/0x1f60 >> [ 61.862376][T11670] ? kernel_write+0x330/0x330 >> [ 61.863221][T11670] ? lockdep_hardirqs_on_prepare+0x43c/0x780 >> [ 61.864230][T11670] ? __fget_files+0x3ea/0x460 >> [ 61.864955][T11670] ? seqcount_lockdep_reader_access+0x157/0x220 >> [ 61.866571][T11670] ? __fdget_pos+0x19e/0x320 >> [ 61.867414][T11670] ksys_write+0x19f/0x2c0 >> [ 61.868263][T11670] ? __ia32_sys_read+0x90/0x90 >> [ 61.868996][T11670] ? ktime_get_coarse_real_ts64+0x10b/0x120 >> [ 61.869896][T11670] do_syscall_64+0xec/0x210 >> [ 61.870592][T11670] entry_SYSCALL_64_after_hwframe+0x67/0x6f >> [ 61.871595][T11670] RIP: 0033:0x472a4f >> [ 61.873158][T11670] Code: 89 54 24 18 48 89 74 24 10 89 7c 24 08 e8 c9 d8 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 0c d9 02 00 48 >> [ 61.876447][T11670] RSP: 002b:00007f7a7a90f5c0 EFLAGS: 00000293 ORIG_RAX: 0000000000000001 >> [ 61.877944][T11670] RAX: ffffffffffffffda RBX: 00007f7a7a911640 RCX: 0000000000472a4f >> [ 61.879751][T11670] RDX: 0000000000000066 RSI: 0000000020000440 RDI: 00000000000000c8 >> [ 61.881100][T11670] RBP: 00007f7a7a90f620 R08: 0000000000000000 R09: 0000000100000000 >> [ 61.882298][T11670] R10: 0000000100000000 R11: 0000000000000293 R12: 00007f7a7a911640 >> [ 61.883501][T11670] R13: 000000000000006e R14: 000000000042f2f0 R15: 00007f7a7a8f1000 >> [ 61.885999][T11670] >> >> Signed-off-by: Radoslaw Zielonek >> --- >> kernel/bpf/cpumap.c | 22 ++++++++++++++++++++++ >> 1 file changed, 22 insertions(+) >> >> diff --git a/kernel/bpf/cpumap.c b/kernel/bpf/cpumap.c >> index a8e34416e960..0034a6d423b6 100644 >> --- a/kernel/bpf/cpumap.c >> +++ b/kernel/bpf/cpumap.c >> @@ -59,6 +59,9 @@ struct bpf_cpu_map_entry { >> u32 cpu; /* kthread CPU and map index */ >> int map_id; /* Back reference to map */ >> >> + /* Used to end ownership transfer transaction */ >> + struct bpf_map *parent_map; >> + >> /* XDP can run multiple RX-ring queues, need __percpu enqueue store */ >> struct xdp_bulk_queue __percpu *bulkq; >> >> @@ -427,6 +430,7 @@ __cpu_map_entry_alloc(struct bpf_map *map, struct bpf_cpumap_val *value, >> rcpu->cpu = cpu; >> rcpu->map_id = map->id; >> rcpu->value.qsize = value->qsize; >> + rcpu->parent_map = map; Is it possible that we increase map reference count here and decrease reference count at __cpu_map_entry_free()? >> >> if (fd > 0 && __cpu_map_load_bpf_program(rcpu, map, fd)) >> goto free_ptr_ring; >> @@ -639,6 +643,14 @@ static int cpu_map_get_next_key(struct bpf_map *map, void *key, void *next_key) >> >> static long cpu_map_redirect(struct bpf_map *map, u64 index, u64 flags) >> { >> + /* >> + * Redirection is a transfer of ownership of the bpf_cpu_map_entry >> + * During the transfer the bpf_cpu_map_entry is still in the map, >> + * so we need to prevent it from being freed. >> + * The bpf_map_inc() increments the refcnt of the map, so the >> + * bpf_cpu_map_entry will not be freed until the refcnt is decremented. >> + */ >> + bpf_map_inc(map); > Adding refcnt increase/decrease in the fast path? Hard NAK. > > The map entry is protected by RCU, which should prevent this kind of UAF > from happening. Looks like maybe there's a bug in the tun driver so this > RCU protection is not working? > > -Toke