On Mon, Jul 09, 2007 at 03:02:02PM +0530, Kalpak Shah wrote:
> Hi Ted,
>
> Recently, one of our customers found this message in pass2 of e2fsck while
> doing some regression testing:
> "Entry '4, 0x695a, 0x81ff, 0x0040, 0x8320, 0xa192, 0x0021' in ??? (136554) has
> rec_len of 14200, should be 26908."
>
> Both the displayed rec_len and the "should be" value are bogus. The
> reason is that salvage_directory sets a offset beyond blocksize
> leading to bogus messages.
Do you have a test case where this happens? I don't think your patch
is right, because if dirent->rec_len is too big, this yes, your patch
will make sure offset doesn't get set beyond fs->blocksize, but it
ends up leaving prev->rec_len also pointing beyond fs->blocksize ---
which means a 2nd e2fsck should result in a complaint about that.
> if (prev && dirent->rec_len && (dirent->rec_len % 4) == 0) {
> prev->rec_len += dirent->rec_len;
^^^^^^^^^^^^^^^^^^^
> - *offset += dirent->rec_len;
> + if (*offset + dirent->rec_len <= fs->blocksize)
> + *offset += dirent->rec_len;
> + else
> + *offset = fs->blocksize;
I think this is a better fix for the problem:
diff --git a/e2fsck/pass2.c b/e2fsck/pass2.c
index e235348..5e088e2 100644
--- a/e2fsck/pass2.c
+++ b/e2fsck/pass2.c
@@ -675,11 +675,12 @@ static void salvage_directory(ext2_filsys fs,
return;
}
/*
- * If the directory entry is a multiple of four, so it is
- * valid, let the previous directory entry absorb the invalid
- * one.
+ * If the record length of the directory entry is a multiple
+ * of four, and not too big, such that it is valid, let the
+ * previous directory entry absorb the invalid one.
*/
- if (prev && dirent->rec_len && (dirent->rec_len % 4) == 0) {
+ if (prev && dirent->rec_len && (dirent->rec_len % 4) == 0 &&
+ (*offset + dirent->rec_len <= fs->blocksize)) {
prev->rec_len += dirent->rec_len;
*offset += dirent->rec_len;
return;
If the dirent->rec_len is too big, then the default salvage method
which follows will do the right thing.
I'd like to have a test case to make sure this works, though, so if
you have a quick test case whipped up, that would be great. Otherwise
I'll have to cons one up when I have a moment.
Thanks, regards,
- Ted
-
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