[PATCH 4.14 61/64] io-mapping: indicate mapping failure

From: Greg Kroah-Hartman
Date: Mon Jul 27 2020 - 10:09:02 EST

From: Michael J. Ruhl <michael.j.ruhl@xxxxxxxxx>

commit e0b3e0b1a04367fc15c07f44e78361545b55357c upstream.

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

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]

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@xxxxxxxxxxxxxxxxxxxx: detect ioremap_wc() errors earlier]

Fixes: cafaf14a5d8f ("io-mapping: Always create a struct to hold metadata about the io-mapping")
Signed-off-by: Michael J. Ruhl <michael.j.ruhl@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxxxxx>
Cc: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Daniel Vetter <daniel@xxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20200721171936.81563-1-michael.j.ruhl@xxxxxxxxx
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

include/linux/io-mapping.h | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

--- a/include/linux/io-mapping.h
+++ b/include/linux/io-mapping.h
@@ -120,9 +120,12 @@ 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)