tree 62cf9d433b59092b20daa55897dc60827940cbff
parent e4b069e0945fa14c71cf8b5b89f8b1b2aa68dbc2
author Mikulas Patocka <mpatocka@redhat.com> 1536153465 -0400
committer Mike Snitzer <snitzer@redhat.com> 1536255069 -0400

dm: disable CRYPTO_TFM_REQ_MAY_SLEEP to fix a GFP_KERNEL recursion deadlock

There's a XFS on dm-crypt deadlock, recursing back to itself due to the
crypto subsystems use of GFP_KERNEL, reported here:
https://bugzilla.kernel.org/show_bug.cgi?id=200835

* dm-crypt calls crypt_convert in xts mode
* init_crypt from xts.c calls kmalloc(GFP_KERNEL)
* kmalloc(GFP_KERNEL) recurses into the XFS filesystem, the filesystem
	tries to submit some bios and wait for them, causing a deadlock

Fix this by updating both the DM crypt and integrity targets to no
longer use the CRYPTO_TFM_REQ_MAY_SLEEP flag, which will change the
crypto allocations from GFP_KERNEL to GFP_ATOMIC, therefore they can't
recurse into a filesystem.  A GFP_ATOMIC allocation can fail, but
init_crypt() in xts.c handles the allocation failure gracefully - it
will fall back to preallocated buffer if the allocation fails.

The crypto API maintainer says that the crypto API only needs to
allocate memory when dealing with unaligned buffers and therefore
turning CRYPTO_TFM_REQ_MAY_SLEEP off is safe (see this discussion:
https://www.redhat.com/archives/dm-devel/2018-August/msg00195.html )

Cc: stable@vger.kernel.org
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>