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89 lines
2.9 KiB
89 lines
2.9 KiB
From: Richard Weinberger <richard@nod.at>
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Date: Wed, 7 Nov 2018 23:04:43 +0100
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Subject: [PATCH] ubifs: Handle re-linking of inodes correctly while recovery
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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UBIFS's recovery code strictly assumes that a deleted inode will never
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come back, therefore it removes all data which belongs to that inode
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as soon it faces an inode with link count 0 in the replay list.
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Before O_TMPFILE this assumption was perfectly fine. With O_TMPFILE
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it can lead to data loss upon a power-cut.
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Consider a journal with entries like:
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0: inode X (nlink = 0) /* O_TMPFILE was created */
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1: data for inode X /* Someone writes to the temp file */
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2: inode X (nlink = 0) /* inode was changed, xattr, chmod, … */
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3: inode X (nlink = 1) /* inode was re-linked via linkat() */
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Upon replay of entry #2 UBIFS will drop all data that belongs to inode X,
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this will lead to an empty file after mounting.
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As solution for this problem, scan the replay list for a re-link entry
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before dropping data.
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Fixes: 474b93704f32 ("ubifs: Implement O_TMPFILE")
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Cc: stable@vger.kernel.org
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Cc: Russell Senior <russell@personaltelco.net>
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Cc: Rafał Miłecki <zajec5@gmail.com>
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Reported-by: Russell Senior <russell@personaltelco.net>
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Reported-by: Rafał Miłecki <zajec5@gmail.com>
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Signed-off-by: Richard Weinberger <richard@nod.at>
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---
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fs/ubifs/replay.c | 37 +++++++++++++++++++++++++++++++++++++
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1 file changed, 37 insertions(+)
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--- a/fs/ubifs/replay.c
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+++ b/fs/ubifs/replay.c
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@@ -210,6 +210,38 @@ static int trun_remove_range(struct ubif
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}
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/**
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+ * inode_still_linked - check whether inode in question will be re-linked.
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+ * @c: UBIFS file-system description object
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+ * @rino: replay entry to test
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+ *
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+ * O_TMPFILE files can be re-linked, this means link count goes from 0 to 1.
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+ * This case needs special care, otherwise all references to the inode will
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+ * be removed upon the first replay entry of an inode with link count 0
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+ * is found.
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+ */
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+static bool inode_still_linked(struct ubifs_info *c, struct replay_entry *rino)
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+{
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+ struct replay_entry *r;
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+
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+ ubifs_assert(c, rino->deletion);
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+ ubifs_assert(c, key_type(c, &rino->key) == UBIFS_INO_KEY);
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+
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+ /*
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+ * Find the most recent entry for the inode behind @rino and check
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+ * whether it is a deletion.
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+ */
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+ list_for_each_entry_reverse(r, &c->replay_list, list) {
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+ ubifs_assert(c, r->sqnum >= rino->sqnum);
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+ if (key_inum(c, &r->key) == key_inum(c, &rino->key))
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+ return r->deletion == 0;
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+
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+ }
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+
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+ ubifs_assert(c, 0);
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+ return false;
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+}
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+
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+/**
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* apply_replay_entry - apply a replay entry to the TNC.
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* @c: UBIFS file-system description object
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* @r: replay entry to apply
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@@ -236,6 +268,11 @@ static int apply_replay_entry(struct ubi
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{
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ino_t inum = key_inum(c, &r->key);
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+ if (inode_still_linked(c, r)) {
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+ err = 0;
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+ break;
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+ }
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+
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err = ubifs_tnc_remove_ino(c, inum);
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break;
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}
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