From patchwork Tue Dec 19 18:29:31 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Omar Sandoval X-Patchwork-Id: 13498844 Received: from mail-pl1-f180.google.com (mail-pl1-f180.google.com [209.85.214.180]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4C02C37D29 for ; Tue, 19 Dec 2023 18:29:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=osandov.com Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=osandov.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=osandov-com.20230601.gappssmtp.com header.i=@osandov-com.20230601.gappssmtp.com header.b="xDakomw+" Received: by mail-pl1-f180.google.com with SMTP id d9443c01a7336-1d3ea5cc137so2219535ad.0 for ; Tue, 19 Dec 2023 10:29:45 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=osandov-com.20230601.gappssmtp.com; s=20230601; t=1703010584; x=1703615384; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=iUQLD57yO7UJihbnG41j52UWyL3ldUoRKMEh2h70H20=; b=xDakomw+iP+qq8siGsMaptZUh+xaFhQ15U8NQuvJKiFH6YTOk1euUwiUZmrXPSguP2 HzpYNRyk3sWjpEt9DIfKiI2a1FZAD6irwfQiIeiZHdFtLua4pWPTy2KoQ7qWGvqYyuJz Mc415b9ZkjCPjatrqPBToCYbiKjKYEPkrhShK8DqtcS+E/63KKMLwKr52jBI3/g9CBiF abyxOmcZ4XEseJ+bNisJl+PPRneXmaMsun47sRLmCqoQvqlmm21OPbcc/9wN79BkcW7m F6LhcYv59LouoxBifgCuwACBUiRTk/UJ8NUMw/l4xSnmZdKnEzbEYHUqKVQcYhw4zraJ cUjA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1703010584; x=1703615384; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=iUQLD57yO7UJihbnG41j52UWyL3ldUoRKMEh2h70H20=; b=jTll0n2KueLrdlSEUm3fgWNdE3ZC8Si36klZtlFXky+4G0zemMLVKfg62T6vrJVDGy Dbc6si560I3mbYLt5gBrd17HU7qE3RPwCc9/CPcGiQhO5UzBJzx7WU46kobkL8k5reEK +OlcipD570R9MJbcCI4dez8Vwt2pWjjIgExj8akUD3OlQ4zdMiZOmVOikiRL45cKT9Ai TCIw2N0T4fo4t5ioK0H2c6EyEopuKCthVeSCjRBnxWM2vgqQyQcz24LkhpIWhMGSE4Jq TF1Nm3NHuH7LGmcOkSa7Y3PlNHWwo2DvcdTNx2zIb+XBPn10ekRxyMpk9Gwt9a7db1EV iJpA== X-Gm-Message-State: AOJu0YwXYmXbUN4vdg2geLc3VgN+0gq3UR+lqTNNRd/eANXFzKrjQ9/k oygXOC1eoz74GTpz3pDFMTZD/pkdxd/CB3ad3W0= X-Google-Smtp-Source: AGHT+IEyT+OTxOL2Lwan8f5y3gFBrxLCDq4/LGXicxfWbeJ4PhZLnH339xZFWPnvxSpXLfbSvo6/rg== X-Received: by 2002:a17:902:d346:b0:1d3:ea02:9ad6 with SMTP id l6-20020a170902d34600b001d3ea029ad6mr488256plk.119.1703010584217; Tue, 19 Dec 2023 10:29:44 -0800 (PST) Received: from telecaster.hsd1.wa.comcast.net ([2620:10d:c090:400::4:649a]) by smtp.gmail.com with ESMTPSA id b14-20020a170902d50e00b001d3e2aac2d4sm1471816plg.29.2023.12.19.10.29.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 19 Dec 2023 10:29:43 -0800 (PST) From: Omar Sandoval To: linux-btrfs@vger.kernel.org Cc: kernel-team@fb.com Subject: [PATCH] btrfs: don't abort filesystem when attempting to snapshot deleted subvolume Date: Tue, 19 Dec 2023 10:29:31 -0800 Message-ID: <068014bd3e90668525c295660862db2932e25087.1703010314.git.osandov@fb.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: Omar Sandoval If the source file descriptor to the snapshot ioctl refers to a deleted subvolume, we get the following abort: ------------[ cut here ]------------ BTRFS: Transaction aborted (error -2) WARNING: CPU: 0 PID: 833 at fs/btrfs/transaction.c:1875 create_pending_snapshot+0x1040/0x1190 [btrfs] Modules linked in: pata_acpi btrfs ata_piix libata scsi_mod virtio_net blake2b_generic xor net_failover virtio_rng failover scsi_common rng_core raid6_pq libcrc32c CPU: 0 PID: 833 Comm: t_snapshot_dele Not tainted 6.7.0-rc6 #2 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-1.fc39 04/01/2014 RIP: 0010:create_pending_snapshot+0x1040/0x1190 [btrfs] Code: e9 44 fe ff ff 44 89 e6 48 c7 c7 f8 59 7b c0 e8 d6 f4 a3 f7 0f 0b e9 4c fa ff ff 44 89 e6 48 c7 c7 f8 59 7b c0 e8 c0 f4 a3 f7 <0f> 0b e9 ef fe ff ff 44 89 e6 48 c7 c7 f8 59 7b c0 e8 aa f4 a3 f7 RSP: 0018:ffffa09c01337af8 EFLAGS: 00010282 RAX: 0000000000000000 RBX: ffff9982053e7c78 RCX: 0000000000000027 RDX: ffff99827dc20848 RSI: 0000000000000001 RDI: ffff99827dc20840 RBP: ffffa09c01337c00 R08: 0000000000000000 R09: ffffa09c01337998 R10: 0000000000000003 R11: ffffffffb96da248 R12: fffffffffffffffe R13: ffff99820535bb28 R14: ffff99820b7bd000 R15: ffff99820381ea80 FS: 00007fe20aadabc0(0000) GS:ffff99827dc00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000559a120b502f CR3: 00000000055b6000 CR4: 00000000000006f0 Call Trace: ? create_pending_snapshot+0x1040/0x1190 [btrfs] ? __warn+0x81/0x130 ? create_pending_snapshot+0x1040/0x1190 [btrfs] ? report_bug+0x171/0x1a0 ? handle_bug+0x3a/0x70 ? exc_invalid_op+0x17/0x70 ? asm_exc_invalid_op+0x1a/0x20 ? create_pending_snapshot+0x1040/0x1190 [btrfs] ? create_pending_snapshot+0x1040/0x1190 [btrfs] create_pending_snapshots+0x92/0xc0 [btrfs] btrfs_commit_transaction+0x66b/0xf40 [btrfs] btrfs_mksubvol+0x301/0x4d0 [btrfs] btrfs_mksnapshot+0x80/0xb0 [btrfs] __btrfs_ioctl_snap_create+0x1c2/0x1d0 [btrfs] btrfs_ioctl_snap_create_v2+0xc4/0x150 [btrfs] btrfs_ioctl+0x8a6/0x2650 [btrfs] ? kmem_cache_free+0x22/0x340 ? do_sys_openat2+0x97/0xe0 __x64_sys_ioctl+0x97/0xd0 do_syscall_64+0x46/0xf0 entry_SYSCALL_64_after_hwframe+0x6e/0x76 RIP: 0033:0x7fe20abe83af Code: 00 48 89 44 24 18 31 c0 48 8d 44 24 60 c7 04 24 10 00 00 00 48 89 44 24 08 48 8d 44 24 20 48 89 44 24 10 b8 10 00 00 00 0f 05 <89> c2 3d 00 f0 ff ff 77 18 48 8b 44 24 18 64 48 2b 04 25 28 00 00 RSP: 002b:00007ffe6eff1360 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 00007fe20abe83af RDX: 00007ffe6eff23c0 RSI: 0000000050009417 RDI: 0000000000000003 RBP: 0000000000000003 R08: 0000000000000000 R09: 00007fe20ad16cd0 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007ffe6eff13c0 R14: 00007fe20ad45000 R15: 0000559a120b6d58 ---[ end trace 0000000000000000 ]--- BTRFS: error (device vdc: state A) in create_pending_snapshot:1875: errno=-2 No such entry BTRFS info (device vdc: state EA): forced readonly BTRFS warning (device vdc: state EA): Skipping commit of aborted transaction. BTRFS: error (device vdc: state EA) in cleanup_transaction:2055: errno=-2 No such entry This happens because create_pending_snapshot() initializes the new root item as a copy of the source root item. This includes the refs field, which is 0 for a deleted subvolume. The call to btrfs_insert_root() therefore inserts a root with refs == 0. btrfs_get_new_fs_root() then finds the root and returns -ENOENT if refs == 0, which causes create_pending_snapshot() to abort. Fix it by checking the source root's refs before attempting the snapshot (but after locking subvol_sem to avoid racing with deletion). Signed-off-by: Omar Sandoval --- Based on misc-next. I'm also sending a regression fstest. Thanks! fs/btrfs/ioctl.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index 4e50b62db2a8..fea5d37528b8 100644 --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -790,6 +790,9 @@ static int create_snapshot(struct btrfs_root *root, struct inode *dir, return -EOPNOTSUPP; } + if (btrfs_root_refs(&root->root_item) == 0) + return -ENOENT; + if (!test_bit(BTRFS_ROOT_SHAREABLE, &root->state)) return -EINVAL;