Guennadi Liakhovetski noticed that the end condition for the loop in bitmap_find_free_region() is wrong, and the "return if error" was also using the wrong conditional that would only trigger if the bitmap was an exact multiple of the allocation size, which is not necessarily the case with dma_alloc_from_coherent(). Such a failure would end up in bitmap_find_free_region() accessing beyond the end of the bitmap.
Showing the changes to lib (1 of 1 file). Show all
Unified · Split
| @@ -948,15 +948,15 @@ done: · 947 unmodified lines | ||
| 948 | 948 | */ |
| 949 | 949 | int bitmap_find_free_region(unsigned long *bitmap, int bits, int order) |
| 950 | 950 | { |
| 951 | − int pos; /* scans bitmap by regions of size order */ | |
| 951 | + int pos, end; /* scans bitmap by regions of size order */ | |
| 952 | 952 | |
| 953 | − for (pos = 0; pos < bits; pos += (1 << order)) | |
| 954 | − if (__reg_op(bitmap, pos, order, REG_OP_ISFREE)) | |
| 955 | − break; | |
| 956 | − if (pos == bits) | |
| 957 | − return -ENOMEM; | |
| 958 | − __reg_op(bitmap, pos, order, REG_OP_ALLOC); | |
| 959 | − return pos; | |
| 953 | + for (pos = 0 ; (end = pos + (1 << order)) <= bits; pos = end) { | |
| 954 | + if (!__reg_op(bitmap, pos, order, REG_OP_ISFREE)) | |
| 955 | + continue; | |
| 956 | + __reg_op(bitmap, pos, order, REG_OP_ALLOC); | |
| 957 | + return pos; | |
| 958 | + } | |
| 959 | + return -ENOMEM; | |
| 960 | 960 | } |
| 961 | 961 | EXPORT_SYMBOL(bitmap_find_free_region); |
| 962 | 962 | |