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Date:   Tue, 12 Jun 2018 11:53:24 +0200
From:   Jan Kara <jack@...e.cz>
To:     <linux-ext4@...r.kernel.org>
Cc:     Ted Tso <tytso@....edu>, Jan Kara <jack@...e.cz>
Subject: [PATCH 06/10] e2fsck: Handle s_inodes_count corruption properly

When s_inodes_count would overflow given number of groups and inodes per
group, we cannot currently fix the breakage in e2fsck as that requires
trimming number of groups or inodes per group which both means data &
inode migration etc. Just trimming sb->s_inodes_count is not enough as
kernel's inode allocation code is not able to handle filesystems where
not all inodes in the last group are usable. So don't pretend we can fix
s_inodes_count overflow by just trimming the s_inodes_count value.

When s_inodes_count is just wrong but will not overflow, let's fix it.
Also move this check before we use s_inodes_count for checking
s_first_ino.

Signed-off-by: Jan Kara <jack@...e.cz>
---
 e2fsck/problem.c |  5 +++++
 e2fsck/problem.h |  2 ++
 e2fsck/super.c   | 27 ++++++++++++++++-----------
 3 files changed, 23 insertions(+), 11 deletions(-)

diff --git a/e2fsck/problem.c b/e2fsck/problem.c
index edc9d51fcf31..8de558edc5dd 100644
--- a/e2fsck/problem.c
+++ b/e2fsck/problem.c
@@ -184,6 +184,11 @@ static struct e2fsck_problem problem_table[] = {
 	  N_("@i count in @S is %i, @s %j.\n"),
 	  PROMPT_FIX, 0 },
 
+	/* Too many inodes in the filesystem */
+	{ PR_0_INODE_COUNT_BIG,
+	  N_("@S would have too many inodes (%N).\n"),
+	  PROMPT_NONE, PR_AFTER_CODE, PR_0_SB_CORRUPT },
+
 	{ PR_0_HURD_CLEAR_FILETYPE,
 	  N_("The Hurd does not support the filetype feature.\n"),
 	  PROMPT_CLEAR, 0 },
diff --git a/e2fsck/problem.h b/e2fsck/problem.h
index 482d111a0f2c..b6bca668bb1b 100644
--- a/e2fsck/problem.h
+++ b/e2fsck/problem.h
@@ -282,6 +282,8 @@ struct problem_context {
 /* Invalid quota inode number */
 #define PR_0_INVALID_QUOTA_INO			0x00004F
 
+/* Inode count in the superblock incorrect */
+#define PR_0_INODE_COUNT_BIG			0x000050
 
 /*
  * Pass 1 errors
diff --git a/e2fsck/super.c b/e2fsck/super.c
index 9c0e0e7b35b4..60a19a7e2767 100644
--- a/e2fsck/super.c
+++ b/e2fsck/super.c
@@ -646,6 +646,22 @@ void check_super_block(e2fsck_t ctx)
 	check_super_value(ctx, "desc_size",
 			  sb->s_desc_size, MAX_CHECK | LOG2_CHECK, 0,
 			  EXT2_MAX_DESC_SIZE);
+
+	should_be = (__u64)sb->s_inodes_per_group * fs->group_desc_count;
+	if (should_be > ~0U) {
+		pctx.num = should_be;
+		fix_problem(ctx, PR_0_INODE_COUNT_BIG, &pctx);
+		ctx->flags |= E2F_FLAG_ABORT;
+		return;
+	}
+	if (sb->s_inodes_count != should_be) {
+		pctx.ino = sb->s_inodes_count;
+		pctx.ino2 = should_be;
+		if (fix_problem(ctx, PR_0_INODE_COUNT_WRONG, &pctx)) {
+			sb->s_inodes_count = should_be;
+			ext2fs_mark_super_dirty(fs);
+		}
+	}
 	if (sb->s_rev_level > EXT2_GOOD_OLD_REV)
 		check_super_value(ctx, "first_ino", sb->s_first_ino,
 				  MIN_CHECK | MAX_CHECK,
@@ -683,17 +699,6 @@ void check_super_block(e2fsck_t ctx)
 		return;
 	}
 
-	should_be = (blk64_t)sb->s_inodes_per_group * fs->group_desc_count;
-	if (should_be > UINT_MAX)
-		should_be = UINT_MAX;
-	if (sb->s_inodes_count != should_be) {
-		pctx.ino = sb->s_inodes_count;
-		pctx.ino2 = should_be;
-		if (fix_problem(ctx, PR_0_INODE_COUNT_WRONG, &pctx)) {
-			sb->s_inodes_count = should_be;
-			ext2fs_mark_super_dirty(fs);
-		}
-	}
 	if (EXT2_INODE_SIZE(sb) > EXT2_GOOD_OLD_INODE_SIZE) {
 		unsigned min =
 			sizeof(((struct ext2_inode_large *) 0)->i_extra_isize) +
-- 
2.13.7

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