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authorRichard Weinberger <richard@nod.at>2018-11-08 01:04:43 +0300
committerRichard Weinberger <richard@nod.at>2018-12-14 00:18:24 +0300
commite58725d51fa8da9133f3f1c54170aa2e43056b91 (patch)
treef0962af31727da74c8696c140f6b5fb9c69b5451
parente542087701f09418702673631a908429feb3eae0 (diff)
downloadlinux-e58725d51fa8da9133f3f1c54170aa2e43056b91.tar.xz
ubifs: Handle re-linking of inodes correctly while recovery
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> Tested-by: Rafał Miłecki <rafal@milecki.pl> Signed-off-by: Richard Weinberger <richard@nod.at>
-rw-r--r--fs/ubifs/replay.c37
1 files changed, 37 insertions, 0 deletions
diff --git a/fs/ubifs/replay.c b/fs/ubifs/replay.c
index a08c5b7030ea..0a0e65c07c6d 100644
--- a/fs/ubifs/replay.c
+++ b/fs/ubifs/replay.c
@@ -213,6 +213,38 @@ static int trun_remove_range(struct ubifs_info *c, struct replay_entry *r)
}
/**
+ * 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(c, rino->deletion);
+ ubifs_assert(c, 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(c, r->sqnum >= rino->sqnum);
+ if (key_inum(c, &r->key) == key_inum(c, &rino->key))
+ return r->deletion == 0;
+
+ }
+
+ ubifs_assert(c, 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 ubifs_info *c, struct replay_entry *r)
{
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;
}