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-rw-r--r--target/linux/generic/backport-4.14/500-ubifs-Handle-re-linking-of-inodes-correctly-while-re.patch89
1 files changed, 89 insertions, 0 deletions
diff --git a/target/linux/generic/backport-4.14/500-ubifs-Handle-re-linking-of-inodes-correctly-while-re.patch b/target/linux/generic/backport-4.14/500-ubifs-Handle-re-linking-of-inodes-correctly-while-re.patch
new file mode 100644
index 0000000000..71e036c920
--- /dev/null
+++ b/target/linux/generic/backport-4.14/500-ubifs-Handle-re-linking-of-inodes-correctly-while-re.patch
@@ -0,0 +1,89 @@
+From: Richard Weinberger <richard@nod.at>
+Date: Wed, 7 Nov 2018 23:04:43 +0100
+Subject: [PATCH] ubifs: Handle re-linking of inodes correctly while recovery
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+UBIFS's recovery code strictly assumes that a deleted inode will never
+come back, therefore it removes all data which belongs to that inode
+as soon it faces an inode with link count 0 in the replay list.
+Before O_TMPFILE this assumption was perfectly fine. With O_TMPFILE
+it can lead to data loss upon a power-cut.
+
+Consider a journal with entries like:
+0: inode X (nlink = 0) /* O_TMPFILE was created */
+1: data for inode X /* Someone writes to the temp file */
+2: inode X (nlink = 0) /* inode was changed, xattr, chmod, … */
+3: inode X (nlink = 1) /* inode was re-linked via linkat() */
+
+Upon replay of entry #2 UBIFS will drop all data that belongs to inode X,
+this will lead to an empty file after mounting.
+
+As solution for this problem, scan the replay list for a re-link entry
+before dropping data.
+
+Fixes: 474b93704f32 ("ubifs: Implement O_TMPFILE")
+Cc: stable@vger.kernel.org
+Cc: Russell Senior <russell@personaltelco.net>
+Cc: Rafał Miłecki <zajec5@gmail.com>
+Reported-by: Russell Senior <russell@personaltelco.net>
+Reported-by: Rafał Miłecki <zajec5@gmail.com>
+Signed-off-by: Richard Weinberger <richard@nod.at>
+---
+ fs/ubifs/replay.c | 37 +++++++++++++++++++++++++++++++++++++
+ 1 file changed, 37 insertions(+)
+
+--- a/fs/ubifs/replay.c
++++ b/fs/ubifs/replay.c
+@@ -210,6 +210,38 @@ static int trun_remove_range(struct ubif
+ }
+
+ /**
++ * inode_still_linked - check whether inode in question will be re-linked.
++ * @c: UBIFS file-system description object
++ * @rino: replay entry to test
++ *
++ * O_TMPFILE files can be re-linked, this means link count goes from 0 to 1.
++ * This case needs special care, otherwise all references to the inode will
++ * be removed upon the first replay entry of an inode with link count 0
++ * is found.
++ */
++static bool inode_still_linked(struct ubifs_info *c, struct replay_entry *rino)
++{
++ struct replay_entry *r;
++
++ ubifs_assert(rino->deletion);
++ ubifs_assert(key_type(c, &rino->key) == UBIFS_INO_KEY);
++
++ /*
++ * Find the most recent entry for the inode behind @rino and check
++ * whether it is a deletion.
++ */
++ list_for_each_entry_reverse(r, &c->replay_list, list) {
++ ubifs_assert(r->sqnum >= rino->sqnum);
++ if (key_inum(c, &r->key) == key_inum(c, &rino->key))
++ return r->deletion == 0;
++
++ }
++
++ ubifs_assert(0);
++ return false;
++}
++
++/**
+ * apply_replay_entry - apply a replay entry to the TNC.
+ * @c: UBIFS file-system description object
+ * @r: replay entry to apply
+@@ -239,6 +271,11 @@ static int apply_replay_entry(struct ubi
+ {
+ ino_t inum = key_inum(c, &r->key);
+
++ if (inode_still_linked(c, r)) {
++ err = 0;
++ break;
++ }
++
+ err = ubifs_tnc_remove_ino(c, inum);
+ break;
+ }