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Commit ba3f75d0 authored by Siddh Raman Pant's avatar Siddh Raman Pant Committed by Yongqiang Liu
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loop: Check for overflow while configuring loop

stable inclusion
from stable-v4.19.257
commit 2035c770bfdbcc82bd52e05871a7c82db9529e0f
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5UQH4
CVE: NA

--------------------------------

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: default avatar <syzbot+a8e049cd3abd342936b6@syzkaller.appspotmail.com>
Cc: stable@vger.kernel.org
Reviewed-by: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: default avatarSiddh Raman Pant <code@siddh.me>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220823160810.181275-1-code@siddh.me


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarYongqiang Liu <liuyongqiang13@huawei.com>
parent c608e294
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......@@ -1354,6 +1354,11 @@ loop_get_status(struct loop_device *lo, struct loop_info64 *info)
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);
......
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