linux-kernel - [PATCH v6] e2fsck: Correct ext4 dates generated by old kernels.

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Date:	Thu, 14 Nov 2013 16:06:33 -0500
From:	David Turner <novalis@...alis.org>
To:	Mark Harris <mhlk@....us>
Cc:	Andreas Dilger <adilger@...ger.ca>, Theodore Ts'o <tytso@....edu>,
	Jan Kara <jack@...e.cz>,
	Ext4 Developers List <linux-ext4@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [PATCH v6] e2fsck: Correct ext4 dates generated by old kernels.

Not sure what the official subject line format is for revising only 
one of N patches, so I'm trying this one.  Let me now if it is wrong.

On Thu, 2013-11-14 at 02:15 -0800, Mark Harris wrote:
> > + * mis-encoded.
> > + */
> > +#define EXT4_EXTRA_NEGATIVE_DATE_CUTOFF 5 * (1ULL << 32)
> 
> Wouldn't 2242 be 0x200000000ULL, i.e. 2 * (1ULL << 32)?

Actually, it would be 2 * (1LL << 32), because we later use it in a
comparison with a signed value.  

--
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 2242).

Signed-off-by: David Turner <novalis@...alis.org>
---
 e2fsck/pass1.c   | 41 +++++++++++++++++++++++++++++++++++++++++
 e2fsck/problem.c |  4 ++++
 e2fsck/problem.h |  4 ++++
 3 files changed, 49 insertions(+)

diff --git a/e2fsck/pass1.c b/e2fsck/pass1.c
index ab23e42..e19855f 100644
--- a/e2fsck/pass1.c
+++ b/e2fsck/pass1.c
@@ -348,6 +348,24 @@ fix:
 				EXT2_INODE_SIZE(sb), "pass1");
 }
 
+#define EXT4_EPOCH_BITS 2
+#define EXT4_EPOCH_MASK ((1 << EXT4_EPOCH_BITS) - 1)
+
+static int check_inode_extra_negative_epoch(__u32 xtime, __u32 extra) {
+	return (xtime & (1 << 31)) != 0 &&
+		(extra & EXT4_EPOCH_MASK) == EXT4_EPOCH_MASK;
+}
+
+#define CHECK_INODE_EXTRA_NEGATIVE_EPOCH(inode, xtime) \
+	check_inode_extra_negative_epoch(inode->i_##xtime, \
+					 inode->i_##xtime##_extra)
+
+/* When today's date is earlier than 2242, we assume that atimes,
+ * ctimes, and mtimes with years in the range 2310..2378 are actually
+ * pre-1970 dates mis-encoded.
+ */
+#define EXT4_EXTRA_NEGATIVE_DATE_CUTOFF 2 * (1LL << 32)
+
 static void check_inode_extra_space(e2fsck_t ctx, struct problem_context *pctx)
 {
 	struct ext2_super_block *sb = ctx->fs->super;
@@ -388,6 +406,29 @@ 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, repair it. 
+	 */
+	if (sizeof(time_t) > 4 && ctx->now < EXT4_EXTRA_NEGATIVE_DATE_CUTOFF &&
+	    (CHECK_INODE_EXTRA_NEGATIVE_EPOCH(inode, atime) ||
+	     CHECK_INODE_EXTRA_NEGATIVE_EPOCH(inode, ctime) ||
+	     CHECK_INODE_EXTRA_NEGATIVE_EPOCH(inode, mtime))) {
+
+		if (!fix_problem(ctx, PR_1_EA_TIME_OUT_OF_RANGE, pctx))
+			return;
+
+		if (CHECK_INODE_EXTRA_NEGATIVE_EPOCH(inode, atime))
+			inode->i_atime_extra &= ~EXT4_EPOCH_MASK;
+		if (CHECK_INODE_EXTRA_NEGATIVE_EPOCH(inode, ctime))
+			inode->i_ctime_extra &= ~EXT4_EPOCH_MASK;
+		if (CHECK_INODE_EXTRA_NEGATIVE_EPOCH(inode, mtime))
+			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..b212d00 100644
--- a/e2fsck/problem.c
+++ b/e2fsck/problem.c
@@ -1018,6 +1018,10 @@ 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 },
 
+  /* Timestamp(s) on inode beyond 2310-04-04 are likely pre-1970 dates. */
+	{ PR_1_EA_TIME_OUT_OF_RANGE,
+		N_("Timestamp(s) on @i %i beyond 2310-04-04 are likely pre-1970 dates.\n"),
+		PROMPT_FIX | PR_PREEN_OK | PR_NO_OK, 0 },
 
 	/* Pass 1b errors */
 
diff --git a/e2fsck/problem.h b/e2fsck/problem.h
index ae1ed26..3710638 100644
--- a/e2fsck/problem.h
+++ b/e2fsck/problem.h
@@ -593,6 +593,10 @@ struct problem_context {
 #define PR_1_EXTENT_INDEX_START_INVALID	0x01006D
 
 #define PR_1_EXTENT_END_OUT_OF_BOUNDS	0x01006E
+
+/* Timestamp(s) on inode beyond 2310-04-04 are likely pre-1970 dates. */
+#define PR_1_EA_TIME_OUT_OF_RANGE	0x01006F
+
 /*
  * Pass 1b errors
  */
-- 
1.8.1.2



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