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authorRobin Murphy <robin.murphy@arm.com>2022-08-15 22:28:40 +0300
committerChristoph Hellwig <hch@lst.de>2022-09-07 11:38:16 +0300
commit2995b8002cefc7b0b00b8f9a0ce36601a8c390c0 (patch)
tree76fe9a7aa5cc776516fdc5d3754fe8a240f3bbc8 /kernel/dma
parent81c12e922b97b94f64e84aa9bfe5a9d1fca2dc25 (diff)
downloadlinux-2995b8002cefc7b0b00b8f9a0ce36601a8c390c0.tar.xz
dma-debug: improve search for partial syncs
When bucket_find_contains() tries to find the original entry for a partial sync, it manages to constrain its search in a way that is both too restrictive and not restrictive enough. A driver which only uses single mappings rather than scatterlists might not set max_seg_size, but could still technically perform a partial sync at an offset of more than 64KB into a sufficiently large mapping, so we could stop searching too early before reaching a legitimate entry. Conversely, if no valid entry is present and max_range is large enough, we can pointlessly search buckets that we've already searched, or that represent an impossible wrapping around the bottom of the address space. At worst, the (legitimate) case of max_seg_size == UINT_MAX can make the loop infinite. Replace the fragile and frankly hard-to-follow "range" logic with a simple counted loop for the number of possible hash buckets below the given address. Reported-by: Yunfei Wang <yf.wang@mediatek.com> Signed-off-by: Robin Murphy <robin.murphy@arm.com> Signed-off-by: Christoph Hellwig <hch@lst.de>
Diffstat (limited to 'kernel/dma')
-rw-r--r--kernel/dma/debug.c6
1 files changed, 2 insertions, 4 deletions
diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c
index 2caafd13f8aa..18c93c2276ca 100644
--- a/kernel/dma/debug.c
+++ b/kernel/dma/debug.c
@@ -350,11 +350,10 @@ static struct dma_debug_entry *bucket_find_contain(struct hash_bucket **bucket,
unsigned long *flags)
{
- unsigned int max_range = dma_get_max_seg_size(ref->dev);
struct dma_debug_entry *entry, index = *ref;
- unsigned int range = 0;
+ int limit = min(HASH_SIZE, (index.dev_addr >> HASH_FN_SHIFT) + 1);
- while (range <= max_range) {
+ for (int i = 0; i < limit; i++) {
entry = __hash_bucket_find(*bucket, ref, containing_match);
if (entry)
@@ -364,7 +363,6 @@ static struct dma_debug_entry *bucket_find_contain(struct hash_bucket **bucket,
* Nothing found, go back a hash bucket
*/
put_hash_bucket(*bucket, *flags);
- range += (1 << HASH_FN_SHIFT);
index.dev_addr -= (1 << HASH_FN_SHIFT);
*bucket = get_hash_bucket(&index, flags);
}