From: Jim Keniston <jkenisto@us.ibm.com>
Date: Mon, 6 Aug 2012 22:46:03 +0000 (-0400)
Subject: e2fsck: fix potential segv when handling a read error in a superblock
X-Git-Tag: v1.43-WIP-2012-09-22~12^2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d45b67c5f2a66597d8e2915052e180203a9193b8;p=thirdparty%2Fe2fsprogs.git

e2fsck: fix potential segv when handling a read error in a superblock

When passed a negative count (indicating a byte count rather than
a block count) e2fsck_handle_read_error() treats the data as a full
block, causing unix_write_blk64() (which can handle negative counts
just fine) to try to write too much.  Given a faulty block device,
this resulted in a SEGV when unix_write_blk64() read past the bottom
of the stack copying the data to cache.  (check_backup_super_block ->
unix_read_blk64 -> raw_read_blk -> e2fsck_handle_read_error)

Reported-by: Alex Friedman <alexfr@il.ibm.com>
Signed-off-by: Jim Keniston <jkenisto@us.ibm.com>
Signed-off-by: Dan Streetman <ddstreet@us.ibm.com>
Reviewed-by: Mingming Cao <mcao@us.ibm.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
---

diff --git a/e2fsck/ehandler.c b/e2fsck/ehandler.c
index 6eecf33f8..6dddf9c17 100644
--- a/e2fsck/ehandler.c
+++ b/e2fsck/ehandler.c
@@ -60,7 +60,7 @@ static errcode_t e2fsck_handle_read_error(io_channel channel,
 	preenhalt(ctx);
 	if (ask(ctx, _("Ignore error"), 1)) {
 		if (ask(ctx, _("Force rewrite"), 1))
-			io_channel_write_blk64(channel, block, 1, data);
+			io_channel_write_blk64(channel, block, count, data);
 		return 0;
 	}