Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
Pre-existing issues: - [High] Truncation of 64-bit DMA addresses to 32-bit unsigned long causes allocator state and memory corruption. - [High] Valid DMA address 0 is treated as an allocation failure, causing a permanent resource leak and kernel panic. -- --- Patch [1]: [PATCH net-next v8 1/3] net: devmem: allow rx-page-size > PAGE_SIZE per dmabuf binding --- commit aedd523e1f497a9daaf91448a092f69629705696 Author: Bobby Eshleman <[email protected]> net: devmem: allow rx-page-size > PAGE_SIZE per dmabuf binding This commit introduces a netlink attribute to allow setting a larger dmabuf rx-page-size for the page_pool. The value must be a power of two and greater than or equal to PAGE_SIZE. > diff --git a/net/core/devmem.c b/net/core/devmem.c > index 957d6b96216b3..f4d60654ce7fd 100644 > --- a/net/core/devmem.c > +++ b/net/core/devmem.c [ ... ] > @@ -87,13 +93,14 @@ struct net_iov * > net_devmem_alloc_dmabuf(struct net_devmem_dmabuf_binding *binding) > { > struct dmabuf_genpool_chunk_owner *owner; > unsigned long dma_addr; > struct net_iov *niov; > ssize_t offset; > ssize_t index; > > - dma_addr = gen_pool_alloc_owner(binding->chunk_pool, PAGE_SIZE, > + dma_addr = gen_pool_alloc_owner(binding->chunk_pool, > + 1UL << binding->niov_shift, > (void **)&owner); > if (!dma_addr) > return NULL; [Severity: High] This isn't a bug introduced by this patch, but does this check incorrectly handle a valid allocation when the dmabuf is mapped at DMA address 0? Since gen_pool_alloc_owner() can return 0 on success if the chunk starts at virtual address 0, checking for !dma_addr might treat a valid DMA address 0 as an allocation failure. This could cause the allocation to leak in the pool without a tracking net_iov. Later, when the dmabuf is unbound, gen_pool_destroy() will check that all chunks are free and could hit a BUG_ON if this allocation was leaked. > > offset = dma_addr - owner->base_dma_addr; > - index = offset / PAGE_SIZE; > + index = offset >> binding->niov_shift; > niov = &owner->area.niovs[index]; [Severity: High] This is a pre-existing issue, but can this lead to an out-of-bounds array access on 32-bit platforms with 64-bit DMA addresses (e.g., LPAE/PAE)? Since dma_addr is derived from gen_pool_alloc_owner(), which returns an unsigned long, it will be a 32-bit value on 32-bit systems. If base_dma_addr is 64-bit and the actual address is above 4GB, the truncated dma_addr subtracted from the 64-bit base_dma_addr would result in a massive underflow. Could this huge offset result in indexing out of bounds when initializing niovs[index]? [ ... ] > @@ -288,7 +295,7 @@ net_devmem_bind_dmabuf(struct net_device *dev, void *vdev, > > owner->area.base_virtual = virtual; > owner->base_dma_addr = dma_addr; > - owner->area.num_niovs = len / PAGE_SIZE; > + owner->area.num_niovs = len >> niov_shift; > owner->binding = binding; > > err = gen_pool_add_owner(binding->chunk_pool, dma_addr, > dma_addr, len, dev_to_node(&dev->dev), > owner); [Severity: High] This isn't a bug introduced by this patch, but does calling gen_pool_add_owner() silently truncate the 64-bit DMA address on 32-bit systems? The gen_pool_add_owner() function takes an unsigned long for the virt argument. When passing dma_addr_t dma_addr on 32-bit architectures, this might truncate the upper 32 bits of the DMA address. If a DMA address exceeds 4GB, could this truncation cause overlapping virtual address ranges in the gen_pool? -- Sashiko AI review ยท https://sashiko.dev/#/patchset/[email protected]?part=1
