linux-ext4 - [PATCH] added sanity check for xattr validation

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Message-ID: <20070226223322.GA30215@schatzie.adilger.int>
Date:	Mon, 26 Feb 2007 15:33:22 -0700
From:	Andreas Dilger <adilger@...sterfs.com>
To:	Theodore Ts'o <tytso@....edu>
Cc:	linux-ext4@...r.kernel.org, Jim Garlick <garlick@...l.gov>
Subject: [PATCH] added sanity check for xattr validation

Ted,
the attached patch adds an extra validity test in check_ext_attr().  If
an attribute's e_value_size is zero the current code does not allocate
a region for it and as a result the e_value_offs value is not verified.
However, if e_value_offs is very large then the later call to
ext2fs_ext_attr_hash_entry() can dereference bad memory and crash e2fsck.

Signed-off-by: Andreas Dilger <adilger@...sterfs.com>
Signed-off-by: Jim Garlick <garlick@...l.gov>

=========================== e_value_offs.patch ============================

Index: e2fsprogs-1.39/e2fsck/pass1.c
===================================================================
--- e2fsprogs-1.39.orig/e2fsck/pass1.c	2007-02-10 15:43:36.000000000 +0530
+++ e2fsprogs-1.39/e2fsck/pass1.c	2007-02-10 15:45:36.000000000 +0530
@@ -1346,6 +1347,11 @@
 			if (fix_problem(ctx, PR_1_EA_BAD_VALUE, pctx))
 				goto clear_extattr;
 		}
+		if (entry->e_value_offs + entry->e_value_size > fs->blocksize) {
+			if (fix_problem(ctx, PR_1_EA_BAD_VALUE, pctx))
+				goto clear_extattr;
+			break;
+		}
 		if (entry->e_value_size &&
 		    region_allocate(region, entry->e_value_offs,
 				    EXT2_EXT_ATTR_SIZE(entry->e_value_size))) {
=========================== e_value_offs.patch ============================

Cheers, Andreas
--
Andreas Dilger
Principal Software Engineer
Cluster File Systems, Inc.

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