From ea5a5af9159cc89e8bcb7a95336e02c8b70aa3d2 Mon Sep 17 00:00:00 2001 From: Rand Deeb Date: Thu, 15 Oct 2026 22:49:35 +0300 Subject: [PATCH] ata: libata-core: Ignore forced transfer modes the host does not support The libata.force parameter can force a transfer mode (pio0-6, mwdma0-4, udma0-7) for a port or device. ata_force_xfermask() applies it in ata_do_set_mode() right after ata_dev_xfermask() has limited the device masks to what the host supports. It replaces those masks with the forced mode without checking the host masks, so a mode the controller does not support is passed to the driver's ->set_piomode() or ->set_dmamode(). Several PATA drivers rely on the host masks to keep the mode number in range when indexing their timing tables. ata_piix, pata_efar, pata_it8213, pata_oldpiix, pata_radisys and pata_rdc declare ATA_PIO4 and ATA_MWDMA12_ONLY, index a five-entry PIO timing table with pio_mode - XFER_PIO_0, and index a three-entry needed_pio[] table with dma_mode - XFER_MW_DMA_0. Booting with libata.force=pio5, pio6, mwdma3 or mwdma4 makes them read past those tables, use the values read as further indices into the timing table, and write the result to the controller's timing registers. Make ata_force_xfermask() skip, with a warning, a forced transfer mode that is not in the port's PIO, MWDMA or UDMA mask, and keep looking for an earlier matching libata.force entry, as it already does for entries that do not apply to the device. With libata.force=pio4,1.0:pio5 on a PIO4 host, device 1.0 now gets pio4 instead of pio5. Forcing a mode the host supports still works as before, including a mode that ata_dev_xfermask() removed for the device or cable. Found by Linux Verification Center (linuxtesting.org) with SVACE. Fixes: 332673257056 ("libata: implement libata.force module parameter") Signed-off-by: Rand Deeb Reviewed-by: Damien Le Moal Link: https://lore.kernel.org/r/20261015194935.1497-1-rand.sec96@gmail.com Signed-off-by: Niklas Cassel --- drivers/ata/libata-core.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c index 00f86abc6bae..dadcaf9ff462 100644 --- a/drivers/ata/libata-core.c +++ b/drivers/ata/libata-core.c @@ -434,6 +434,7 @@ static void ata_force_link_limits(struct ata_link *link) */ static void ata_force_xfermask(struct ata_device *dev) { + struct ata_port *ap = dev->link->ap; int devno = dev->link->pmp + dev->devno; int alt_devno = devno; int i; @@ -458,6 +459,17 @@ static void ata_force_xfermask(struct ata_device *dev) ata_unpack_xfermask(fe->param.xfer_mask, &pio_mask, &mwdma_mask, &udma_mask); + + /* Make sure that the port supports the specified xfer modes. */ + if (!(pio_mask & ap->pio_mask) && + !(mwdma_mask & ap->mwdma_mask) && + !(udma_mask & ap->udma_mask)) { + ata_dev_warn(dev, + "FORCE: ignoring unsupported xfer_mask %s\n", + fe->param.name); + continue; + } + if (udma_mask) dev->udma_mask = udma_mask; else if (mwdma_mask) {