[PATCH v4 2/2] e2fsck: Correct ext4 dates generated by old kernels.

[David Turner <novalis@novalis.org>]

This patch is against e2fsprogs.

---
Older kernels on 64-bit machines would incorrectly encode pre-1970
ext4 dates as post-2311 dates.  Detect and correct this (assuming the
current date is before 2311).

Signed-off-by: David Turner <novalis@novalis.org>
---
 e2fsck/pass1.c   | 37 +++++++++++++++++++++++++++++++++++++
 e2fsck/problem.c |  7 +++++++
 e2fsck/problem.h |  6 ++++++
 3 files changed, 50 insertions(+)

diff --git a/e2fsck/pass1.c b/e2fsck/pass1.c
index ab23e42..cb72964 100644
--- a/e2fsck/pass1.c
+++ b/e2fsck/pass1.c
@@ -348,6 +348,23 @@ fix:
 				EXT2_INODE_SIZE(sb), "pass1");
 }
 
+#define EXT4_EPOCH_BITS 2
+#define EXT4_EPOCH_MASK ((1 << EXT4_EPOCH_BITS) - 1)
+
+static int large_inode_extra(__u32 xtime, __u32 extra) {
+	return (xtime & (1 << 31)) != 0 &&
+		(extra & EXT4_EPOCH_MASK) == EXT4_EPOCH_MASK;
+}
+
+#define LARGE_INODE_EXTRA(inode, xtime) \
+	large_inode_extra(inode->i_##xtime, \
+			  inode->i_##xtime##_extra)
+
+/* When the date is earlier than 2311, we assume that atimes, ctimes,
+ * and mtimes greater than 2311 are actually pre-1970 dates mis-encoded.
+ */
+#define EXT4_EXTRA_NEGATIVE_DATE_CUTOFF 6 * (1UL << 32)
+
 static void check_inode_extra_space(e2fsck_t ctx, struct problem_context *pctx)
 {
 	struct ext2_super_block *sb = ctx->fs->super;
@@ -388,6 +405,26 @@ static void check_inode_extra_space(e2fsck_t ctx, struct problem_context *pctx)
 		/* it seems inode has an extended attribute(s) in body */
 		check_ea_in_inode(ctx, pctx);
 	}
+
+	/*
+	 * If the inode's extended atime (ctime, mtime) is stored in
+	 * the old, invalid format, the inode is corrupt.
+	 */
+	if (sizeof(time_t) > 4 && ctx->now < EXT4_EXTRA_NEGATIVE_DATE_CUTOFF &&
+		LARGE_INODE_EXTRA(inode, atime) ||
+		LARGE_INODE_EXTRA(inode, ctime) ||
+		LARGE_INODE_EXTRA(inode, mtime)) {
+
+		if (!fix_problem(ctx, PR_1_EA_TIME_OUT_OF_RANGE, pctx))
+			return;
+
+		inode->i_atime_extra &= ~EXT4_EPOCH_MASK;
+		inode->i_ctime_extra &= ~EXT4_EPOCH_MASK;
+		inode->i_mtime_extra &= ~EXT4_EPOCH_MASK;
+		e2fsck_write_inode_full(ctx, pctx->ino, pctx->inode,
+					EXT2_INODE_SIZE(sb), "pass1");
+	}
+
 }
 
 /*
diff --git a/e2fsck/problem.c b/e2fsck/problem.c
index 897693a..51fa7c3 100644
--- a/e2fsck/problem.c
+++ b/e2fsck/problem.c
@@ -1018,6 +1018,13 @@ static struct e2fsck_problem problem_table[] = {
 	  N_("@i %i, end of extent exceeds allowed value\n\t(logical @b %c, physical @b %b, len %N)\n"),
 	  PROMPT_CLEAR, 0 },
 
+/* The extended a, c, or mtime on this inode is in the far future,
+   indicating that it was written with an older, buggy version of the
+   kernel on a 64-bit machine */
+	{ PR_1_EA_TIME_OUT_OF_RANGE,
+	  N_("Extended time on @i %i is in the far future.\n"
+		"Assume that it is in fact a pre-1970 date written by an older, buggy version of Linux?\n"), 
+		PROMPT_FIX, 0 },
 
 	/* Pass 1b errors */
 
diff --git a/e2fsck/problem.h b/e2fsck/problem.h
index ae1ed26..a44f6dd 100644
--- a/e2fsck/problem.h
+++ b/e2fsck/problem.h
@@ -593,6 +593,12 @@ struct problem_context {
 #define PR_1_EXTENT_INDEX_START_INVALID	0x01006D
 
 #define PR_1_EXTENT_END_OUT_OF_BOUNDS	0x01006E
+
+/* The extended a, c, or mtime on this inode is in the far future,
+   indicating that it was written with an older, buggy version of
+	 the kernel on a 64-bit machine */
+#define PR_1_EA_TIME_OUT_OF_RANGE	0x01006F
+
 /*
  * Pass 1b errors
  */
-- 
1.8.1.2