linux-ext4 - [PATCH v3] e2fsck: do not read EA header beyond the end of an inode

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Message-Id: <1448571594-32225-1-git-send-email-artemiyv@acm.org>
Date:	Thu, 26 Nov 2015 20:59:54 +0000
From:	Artemiy Volkov <artemiyv@....org>
To:	linux-ext4@...r.kernel.org
Cc:	Artemiy Volkov <artemiyv@....org>
Subject: [PATCH v3] e2fsck: do not read EA header beyond the end of an inode

In check_inode_extra_space(), if we attempt to read an EA header at
the end of the extra space, in a corrupted filesystem it may result in
a read beyond the bounds of the inode. Add a check to prevent this.

Reproduced by running ./test_one --valgrind f_write_ea_toobig_extra_isize.

Signed-off-by: Artemiy Volkov <artemiyv@....org>
---

A quick fix to v1 which wrongly uses spaces instead of tabs.
Correct a nonexistent struct ext2_inode_large field name used in v2.

 e2fsck/pass1.c |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/e2fsck/pass1.c b/e2fsck/pass1.c
index 0a8e23e..71ea943 100644
--- a/e2fsck/pass1.c
+++ b/e2fsck/pass1.c
@@ -482,6 +482,10 @@ static void check_inode_extra_space(e2fsck_t ctx, struct problem_context *pctx)
 		return;
 	}
 
+	/* check if there is no place for an EA header */
+	if (inode->i_extra_isize >= max - sizeof(__u32))
+		return;
+
 	eamagic = (__u32 *) (((char *) inode) + EXT2_GOOD_OLD_INODE_SIZE +
 			inode->i_extra_isize);
 	if (*eamagic == EXT2_EXT_ATTR_MAGIC) {
-- 
1.7.10.4

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