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loop: Check for overflow while configuring loop

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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: [email protected]
Cc: [email protected]
Reviewed-by: Matthew Wilcox (Oracle) <[email protected]>
Signed-off-by: Siddh Raman Pant <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
This commit is contained in:
Siddh Raman Pant 2022-08-23 21:38:10 +05:30 • committed by Greg Kroah-Hartman
commit 13b2856037
1 changed files with 5 additions and 0 deletions
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5
drivers/block/loop.c
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@ -1397,6 +1397,11 @@ 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);