This is a note to let you know that I've just added the patch titled
loop: Check for overflow while configuring loop
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
loop-check-for-overflow-while-configuring-loop.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From c490a0b5a4f36da3918181a8acdc6991d967c5f3 Mon Sep 17 00:00:00 2001
From: Siddh Raman Pant <code@xxxxxxxx>
Date: Tue, 23 Aug 2022 21:38:10 +0530
Subject: loop: Check for overflow while configuring loop
From: Siddh Raman Pant <code@xxxxxxxx>
commit c490a0b5a4f36da3918181a8acdc6991d967c5f3 upstream.
The userspace can configure a loop using an ioctl call, wherein
a configuration of type loop_config is passed (see lo_ioctl()'s
case on line 1550 of drivers/block/loop.c). This proceeds to call
loop_configure() which in turn calls loop_set_status_from_info()
(see line 1050 of loop.c), passing &config->info which is of type
loop_info64*. This function then sets the appropriate values, like
the offset.
loop_device has lo_offset of type loff_t (see line 52 of loop.c),
which is typdef-chained to long long, whereas loop_info64 has
lo_offset of type __u64 (see line 56 of include/uapi/linux/loop.h).
The function directly copies offset from info to the device as
follows (See line 980 of loop.c):
lo->lo_offset = info->lo_offset;
This results in an overflow, which triggers a warning in iomap_iter()
due to a call to iomap_iter_done() which has:
WARN_ON_ONCE(iter->iomap.offset > iter->pos);
Thus, check for negative value during loop_set_status_from_info().
Bug report: https://syzkaller.appspot.com/bug?id=c620fe14aac810396d3c3edc9ad73848bf69a29e
Reported-and-tested-by: syzbot+a8e049cd3abd342936b6@xxxxxxxxxxxxxxxxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Reviewed-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Signed-off-by: Siddh Raman Pant <code@xxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Link: https://lore.kernel.org/r/20220823160810.181275-1-code@xxxxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/block/loop.c | 5 +++++
1 file changed, 5 insertions(+)
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1351,6 +1351,11 @@ loop_get_status(struct loop_device *lo,
info->lo_number = lo->lo_number;
info->lo_offset = lo->lo_offset;
info->lo_sizelimit = lo->lo_sizelimit;
+
+ /* loff_t vars have been assigned __u64 */
+ if (lo->lo_offset < 0 || lo->lo_sizelimit < 0)
+ return -EOVERFLOW;
+
info->lo_flags = lo->lo_flags;
memcpy(info->lo_file_name, lo->lo_file_name, LO_NAME_SIZE);
memcpy(info->lo_crypt_name, lo->lo_crypt_name, LO_NAME_SIZE);
Patches currently in stable-queue which might be from code@xxxxxxxx are
queue-4.19/loop-check-for-overflow-while-configuring-loop.patch
