From: "Michael J. Ruhl" michael.j.ruhl@intel.com Subject: io-mapping: indicate mapping failure
The !ATOMIC_IOMAP version of io_maping_init_wc will always return success, even when the ioremap fails.
Since the ATOMIC_IOMAP version returns NULL when the init fails, and callers check for a NULL return on error this is unexpected.
During a device probe, where the ioremap failed, a crash can look like this:
BUG: unable to handle page fault for address: 0000000000210000 #PF: supervisor write access in kernel mode #PF: error_code(0x0002) - not-present page Oops: 0002 [#1] PREEMPT SMP CPU: 0 PID: 177 Comm: RIP: 0010:fill_page_dma [i915] gen8_ppgtt_create [i915] i915_ppgtt_create [i915] intel_gt_init [i915] i915_gem_init [i915] i915_driver_probe [i915] pci_device_probe really_probe driver_probe_device
The remap failure occurred much earlier in the probe. If it had been propagated, the driver would have exited with an error.
Return NULL on ioremap failure.
[akpm@linux-foundation.org: detect ioremap_wc() errors earlier] Link: http://lkml.kernel.org/r/20200721171936.81563-1-michael.j.ruhl@intel.com Fixes: cafaf14a5d8f ("io-mapping: Always create a struct to hold metadata about the io-mapping") Signed-off-by: Michael J. Ruhl michael.j.ruhl@intel.com Reviewed-by: Andrew Morton akpm@linux-foundation.org Cc: Mike Rapoport rppt@linux.ibm.com Cc: Andy Shevchenko andriy.shevchenko@linux.intel.com Cc: Chris Wilson chris@chris-wilson.co.uk Cc: Daniel Vetter daniel@ffwll.ch Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
include/linux/io-mapping.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
--- a/include/linux/io-mapping.h~io-mapping-indicate-mapping-failure +++ a/include/linux/io-mapping.h @@ -107,9 +107,12 @@ io_mapping_init_wc(struct io_mapping *io resource_size_t base, unsigned long size) { + iomap->iomem = ioremap_wc(base, size); + if (!iomap->iomem) + return NULL; + iomap->base = base; iomap->size = size; - iomap->iomem = ioremap_wc(base, size); #if defined(pgprot_noncached_wc) /* archs can't agree on a name ... */ iomap->prot = pgprot_noncached_wc(PAGE_KERNEL); #elif defined(pgprot_writecombine) _