linux-kernel - [PATCH 5.7 165/179] io-mapping: indicate mapping failure

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Date:   Mon, 27 Jul 2020 16:05:40 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        "Michael J. Ruhl" <michael.j.ruhl@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        Daniel Vetter <daniel@...ll.ch>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 5.7 165/179] io-mapping: indicate mapping failure

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

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
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@...ux-foundation.org: 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@...el.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Reviewed-by: Andrew Morton <akpm@...ux-foundation.org>
Cc: Mike Rapoport <rppt@...ux.ibm.com>
Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Chris Wilson <chris@...is-wilson.co.uk>
Cc: Daniel Vetter <daniel@...ll.ch>
Cc: <stable@...r.kernel.org>
Link: http://lkml.kernel.org/r/20200721171936.81563-1-michael.j.ruhl@intel.com
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 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
@@ -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)