linux-ext4 - [PATCH] e2fsprogs: e2fsck_handle_read_error

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Date:	Mon, 06 Aug 2012 13:05:53 -0700
From:	Jim Keniston <jkenisto@...ibm.com>
To:	tytso@....edu, linux-ext4@...r.kernel.org
Cc:	ddstreet@...ibm.com, mcao@...ibm.com, alexfr@...ibm.com
Subject: [PATCH] e2fsprogs: e2fsck_handle_read_error - pass along negative
	count

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)

Signed-off-by: Jim Keniston <jkenisto@...ibm.com>
Signed-off-by: Dan Streetman <ddstreet@...ibm.com>
Reviewed-by: Mingming Cao <mcao@...ibm.com>
Reported-by: Alex Friedman <alexfr@...ibm.com>
---

 e2fsck/ehandler.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/e2fsck/ehandler.c b/e2fsck/ehandler.c
index 6eecf33..6dddf9c 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;
 	}
 

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