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[125.237.197.94]) by smtp.gmail.com with ESMTPSA id n23sm443798pff.93.2021.06.22.17.44.42 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 22 Jun 2021 17:44:43 -0700 (PDT) From: Matthew Ruffell To: kernel-team@lists.ubuntu.com Subject: [SRU][B][PATCH 1/2] Revert "btrfs: reloc: fix reloc root leak and NULL pointer dereference" Date: Wed, 23 Jun 2021 12:44:32 +1200 Message-Id: <20210623004433.22819-2-matthew.ruffell@canonical.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210623004433.22819-1-matthew.ruffell@canonical.com> References: <20210623004433.22819-1-matthew.ruffell@canonical.com> MIME-Version: 1.0 X-BeenThere: kernel-team@lists.ubuntu.com X-Mailman-Version: 2.1.20 Precedence: list List-Id: Kernel team discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: kernel-team-bounces@lists.ubuntu.com Sender: "kernel-team" BugLink: https://bugs.launchpad.net/bugs/1933172 This reverts commit 6f536ce7a978531d38a21d092394616cefb54436. A mistake was made in the backport of "btrfs: reloc: fix reloc root leak and NULL pointer dereference" to Bionic, and this commit reverts the changes, so we can fix them in the next commit. If you attempt to balance a btrfs filesystem where root nodes need to be relocated, some root nodes were mistakenly freed with calls to btrfs_put_fs_root(), which leads to a general protection fault when we try to access those root nodes when we try and commit the balance transaction. This results in the following stack trace: general protection fault: 0000 [#1] SMP PTI CPU: 0 PID: 18440 Comm: btrfs Not tainted 4.15.0-136-generic #140-Ubuntu RIP: 0010:btrfs_set_root_node+0x5/0x60 [btrfs] Call Trace: ? commit_fs_roots+0x130/0x1b0 [btrfs] ? btrfs_run_delayed_refs.part.70+0x80/0x190 [btrfs] btrfs_commit_transaction+0x42c/0x910 [btrfs] ? start_transaction+0x191/0x430 [btrfs] relocate_block_group+0x1e7/0x640 [btrfs] btrfs_relocate_block_group+0x18f/0x280 [btrfs] btrfs_relocate_chunk+0x38/0xd0 [btrfs] __btrfs_balance+0x972/0xcd0 [btrfs] ? insert_balance_item.isra.35+0x391/0x3c0 [btrfs] btrfs_balance+0x32c/0x5a0 [btrfs] btrfs_ioctl_balance+0x320/0x390 [btrfs] btrfs_ioctl+0x5a6/0x2490 [btrfs] ? lru_cache_add_active_or_unevictable+0x36/0xb0 ? __handle_mm_fault+0x9fd/0x1290 do_vfs_ioctl+0xa8/0x630 ? btrfs_ioctl_get_supported_features+0x30/0x30 [btrfs] ? do_vfs_ioctl+0xa8/0x630 ? __do_page_fault+0x2a1/0x4b0 SyS_ioctl+0x79/0x90 do_syscall_64+0x73/0x130 entry_SYSCALL_64_after_hwframe+0x41/0xa6 Revert the changes, so we can apply the correct backport in the next patch. Signed-off-by: Matthew Ruffell --- fs/btrfs/relocation.c | 16 +++------------- 1 file changed, 3 insertions(+), 13 deletions(-) diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c index b227c4c57cd8..95bc0ee66c03 100644 --- a/fs/btrfs/relocation.c +++ b/fs/btrfs/relocation.c @@ -2444,10 +2444,12 @@ void merge_reloc_roots(struct reloc_control *rc) reloc_root = list_entry(reloc_roots.next, struct btrfs_root, root_list); - root = read_fs_root(fs_info, reloc_root->root_key.offset); if (btrfs_root_refs(&reloc_root->root_item) > 0) { + root = read_fs_root(fs_info, + reloc_root->root_key.offset); BUG_ON(IS_ERR(root)); BUG_ON(root->reloc_root != reloc_root); + ret = merge_reloc_root(rc, root); if (ret) { if (list_empty(&reloc_root->root_list)) @@ -2456,18 +2458,6 @@ void merge_reloc_roots(struct reloc_control *rc) goto out; } } else { - if (!IS_ERR(root)) { - if (root->reloc_root == reloc_root) { - root->reloc_root = NULL; - free_extent_buffer(root->reloc_root->node); - free_extent_buffer(root->reloc_root->commit_root); - btrfs_put_fs_root(reloc_root); - } - free_extent_buffer(root->node); - free_extent_buffer(root->commit_root); - btrfs_put_fs_root(root); - } - list_del_init(&reloc_root->root_list); }