s390/dasd: Guard sysfs discipline callbacks against unallocated private data

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Several sysfs show/store handlers call a discipline callback that
dereferences device->private, either directly or through the
DASD_DEFINE_ATTR() macro. During dasd_generic_set_online() the discipline
is assigned before check_device() allocates device->private, so an
unprivileged read of one of these world-readable attributes in that window
dereferences a NULL pointer and panics.

Guard the dereference inside each callback that actually touches
device->private.

Fixes: c729696bcf ("s390/dasd: Recognise data for ESE volumes")
Cc: stable@vger.kernel.org
Reviewed-by: Jan Höppner <hoeppner@linux.ibm.com>
Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
Link: https://patch.msgid.link/20260805111612.1285190-4-sth@linux.ibm.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

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Stefan Haberland 2026-08-05 13:15:56 +02:00 • committed by Jens Axboe

parent 6fb5ba2e7e

commit 2a1780f9fc

1 changed files with 38 additions and 2 deletions

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drivers/s390/block/dasd_eckd.c

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