dma-debug: fix locking bug in check_unmap()

In check_unmap() it is possible to get into a dead-locked state if
dma_mapping_error is called.  The problem is that the bucket is locked in
check_unmap, and locked again by debug_dma_mapping_error which is called
by dma_mapping_error.  To resolve that we must release the lock on the
bucket before making the call to dma_mapping_error.

[akpm@linux-foundation.org: restore 80-col trickery to be consistent with the rest of the file]
Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Cc: Joerg Roedel <joro@8bytes.org>
Reviewed-by: Shuah Khan <shuah.khan@hp.com>
Tested-by: Shuah Khan <shuah.khan@hp.com>
Cc: Jakub Kicinski <kubakici@wp.pl>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 12 insertions, 9 deletions

diff --git a/lib/dma-debug.c b/lib/dma-debug.c
index 5e396accd3d0..d3e06a5e981e 100644
--- a/lib/dma-debug.c
+++ b/lib/dma-debug.c
@@ -862,17 +862,21 @@ static void check_unmap(struct dma_debug_entry *ref)
         entry = bucket_find_exact(bucket, ref);
 
         if (!entry) {
+                /* must drop lock before calling dma_mapping_error */
+                put_hash_bucket(bucket, &flags);
+
                 if (dma_mapping_error(ref->dev, ref->dev_addr)) {
                         err_printk(ref->dev, NULL,
-                                   "DMA-API: device driver tries "
-                                   "to free an invalid DMA memory address\n");
-                        return;
+                                   "DMA-API: device driver tries to free an "
+                                   "invalid DMA memory address\n");
+                } else {
+                        err_printk(ref->dev, NULL,
+                                   "DMA-API: device driver tries to free DMA "
+                                   "memory it has not allocated [device "
+                                   "address=0x%016llx] [size=%llu bytes]\n",
+                                   ref->dev_addr, ref->size);
                 }
-                err_printk(ref->dev, NULL, "DMA-API: device driver tries "
-                           "to free DMA memory it has not allocated "
-                           "[device address=0x%016llx] [size=%llu bytes]\n",
-                           ref->dev_addr, ref->size);
-                goto out;
+                return;
         }
 
         if (ref->size != entry->size) {
@@ -936,7 +940,6 @@ static void check_unmap(struct dma_debug_entry *ref)
         hash_bucket_del(entry);
         dma_entry_free(entry);
 
-out:
         put_hash_bucket(bucket, &flags);
 }