From: Junrui Luo Date: Tue, 2 Jun 2026 08:58:48 +0000 (+0800) Subject: vfio: prevent infinite loop in vfio_mig_get_next_state() on blocked arc X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a26b499b757cfc8bbff1088bb1b844639e250893;p=thirdparty%2Flinux.git vfio: prevent infinite loop in vfio_mig_get_next_state() on blocked arc vfio_mig_get_next_state() walks vfio_from_fsm_table[] one step at a time, looping to skip optional states the device does not support until *next_fsm is supported. A blocked transition is encoded as VFIO_DEVICE_STATE_ERROR, which the trailing return reports as -EINVAL. The skip loop does not account for the ERROR sentinel. state_flags_table[ERROR] is ~0U and vfio_from_fsm_table[ERROR][*] is ERROR, so once *next_fsm becomes ERROR the loop condition stays true and *next_fsm never changes. The blocked arcs STOP_COPY -> PRE_COPY and STOP_COPY -> PRE_COPY_P2P map to ERROR yet pass the support check on a precopy-capable device, causing the loop to spin forever while holding the driver state mutex. This can result in a soft lockup, and a panic with softlockup_panic set. Terminate the skip loop on the ERROR sentinel so a blocked transition falls through to the existing return and reports -EINVAL. Fixes: 4db52602a607 ("vfio: Extend the device migration protocol with PRE_COPY") Reported-by: Yuhao Jiang Cc: stable@vger.kernel.org Signed-off-by: Junrui Luo Reviewed-by: Kevin Tian Reviewed-by: Jason Gunthorpe Link: https://lore.kernel.org/r/SYBPR01MB7881290BBDE79B61AE6A017FAF122@SYBPR01MB7881.ausprd01.prod.outlook.com Signed-off-by: Alex Williamson --- diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c index 6222376ab6ab..5e0422014523 100644 --- a/drivers/vfio/vfio_main.c +++ b/drivers/vfio/vfio_main.c @@ -858,7 +858,8 @@ int vfio_mig_get_next_state(struct vfio_device *device, * logical state, as per the above comment. */ *next_fsm = vfio_from_fsm_table[cur_fsm][new_fsm]; - while ((state_flags_table[*next_fsm] & device->migration_flags) != + while (*next_fsm != VFIO_DEVICE_STATE_ERROR && + (state_flags_table[*next_fsm] & device->migration_flags) != state_flags_table[*next_fsm]) *next_fsm = vfio_from_fsm_table[*next_fsm][new_fsm];