| Message ID | 20220730114146.32669-1-yf.wang@mediatek.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | dma-debug: Fix overflow issue in bucket_find_contain | expand |
> + unsigned int shift = (1 << HASH_FN_SHIFT);
Please just add a constant for that right nxt to the HASH_FN_SHIFT
definition.
On 2022-07-30 12:41, yf.wang@mediatek.com wrote: > From: Yunfei Wang <yf.wang@mediatek.com> > > There are two issue: > 1. If max_rang is set to 0xFFFF_FFFF, and __hash_bucket_find always > returns NULL, the rang will be accumulated. When rang is accumulated > to 0xFFFF_E000, after executing rang += (1 << HASH_FN_SHIFT) again, > rang will overflow to 0, making it impossible to exit the while loop. > 2. dev_addr reduce maybe overflow. > > So, add range and dev_addr check to avoid overflow. > > Signed-off-by: jianjiao zeng <jianjiao.zeng@mediatek.com> > Signed-off-by: Yunfei Wang <yf.wang@mediatek.com> > --- > kernel/dma/debug.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c > index ad731f7858c9..9d7d54cd4c63 100644 > --- a/kernel/dma/debug.c > +++ b/kernel/dma/debug.c > @@ -352,6 +352,7 @@ static struct dma_debug_entry *bucket_find_contain(struct hash_bucket **bucket, > > unsigned int max_range = dma_get_max_seg_size(ref->dev); > struct dma_debug_entry *entry, index = *ref; > + unsigned int shift = (1 << HASH_FN_SHIFT); > unsigned int range = 0; > > while (range <= max_range) { > @@ -360,12 +361,15 @@ static struct dma_debug_entry *bucket_find_contain(struct hash_bucket **bucket, > if (entry) > return entry; > > + if (max_range - range < shift || index.dev_addr < shift) > + return NULL; This seems a bit clunky since the first condition here effectively makes the loop condition redundant. FWIW I found the whole "range" business here rather hard to make sense of - personally I'd calculate a lower bound for the address then just iterate down to that, but maybe that's just me :/ Otherwise, at the very least we should be capping max_range so that the loop doesn't go beyond HASH_SIZE iterations and pointlessly search the same buckets more than once - it's stupid to even *get* to the point of having to worry about that overflowing. Whether we really care about dev_addr underflow is then another matter. Really it would seem even more logical to make this a lower-level function that can walk round the dma_entry_hash array directly and not have to monkey about with the fake "index" entry at all, but cleaning up the almost-unnecessary amount of internal abstractions here is maybe more work than it's worth at this point. Robin. > + > /* > * Nothing found, go back a hash bucket > */ > put_hash_bucket(*bucket, *flags); > - range += (1 << HASH_FN_SHIFT); > - index.dev_addr -= (1 << HASH_FN_SHIFT); > + range += shift; > + index.dev_addr -= shift; > *bucket = get_hash_bucket(&index, flags); > } >
diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c index ad731f7858c9..9d7d54cd4c63 100644 --- a/kernel/dma/debug.c +++ b/kernel/dma/debug.c @@ -352,6 +352,7 @@ static struct dma_debug_entry *bucket_find_contain(struct hash_bucket **bucket, unsigned int max_range = dma_get_max_seg_size(ref->dev); struct dma_debug_entry *entry, index = *ref; + unsigned int shift = (1 << HASH_FN_SHIFT); unsigned int range = 0; while (range <= max_range) { @@ -360,12 +361,15 @@ static struct dma_debug_entry *bucket_find_contain(struct hash_bucket **bucket, if (entry) return entry; + if (max_range - range < shift || index.dev_addr < shift) + return NULL; + /* * Nothing found, go back a hash bucket */ put_hash_bucket(*bucket, *flags); - range += (1 << HASH_FN_SHIFT); - index.dev_addr -= (1 << HASH_FN_SHIFT); + range += shift; + index.dev_addr -= shift; *bucket = get_hash_bucket(&index, flags); }