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@xxxxxxxxxxxxx>
Signed-off-by: Jim Garlick <garlick@xxxxxxxx>
=========================== 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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