KMSAN doesn't know about DMA memory writes performed by devices. We unpoison such memory when it's mapped to avoid false positive reports. Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx> --- v2: -- move implementation of kmsan_handle_dma() and kmsan_handle_dma_sg() here v4: -- swap dma: and kmsan: int the subject v5: -- do not export KMSAN hooks that are not called from modules v6: -- add a missing #include <linux/kmsan.h> Link: https://linux-review.googlesource.com/id/Ia162dc4c5a92e74d4686c1be32a4dfeffc5c32cd --- include/linux/kmsan.h | 41 ++++++++++++++++++++++++++++++ kernel/dma/mapping.c | 10 +++++--- mm/kmsan/hooks.c | 59 +++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 107 insertions(+), 3 deletions(-) diff --git a/include/linux/kmsan.h b/include/linux/kmsan.h index e00de976ee438..dac296da45c55 100644 --- a/include/linux/kmsan.h +++ b/include/linux/kmsan.h @@ -9,6 +9,7 @@ #ifndef _LINUX_KMSAN_H #define _LINUX_KMSAN_H +#include <linux/dma-direction.h> #include <linux/gfp.h> #include <linux/kmsan-checks.h> #include <linux/types.h> @@ -16,6 +17,7 @@ struct page; struct kmem_cache; struct task_struct; +struct scatterlist; #ifdef CONFIG_KMSAN @@ -172,6 +174,35 @@ void kmsan_ioremap_page_range(unsigned long addr, unsigned long end, */ void kmsan_iounmap_page_range(unsigned long start, unsigned long end); +/** + * kmsan_handle_dma() - Handle a DMA data transfer. + * @page: first page of the buffer. + * @offset: offset of the buffer within the first page. + * @size: buffer size. + * @dir: one of possible dma_data_direction values. + * + * Depending on @direction, KMSAN: + * * checks the buffer, if it is copied to device; + * * initializes the buffer, if it is copied from device; + * * does both, if this is a DMA_BIDIRECTIONAL transfer. + */ +void kmsan_handle_dma(struct page *page, size_t offset, size_t size, + enum dma_data_direction dir); + +/** + * kmsan_handle_dma_sg() - Handle a DMA transfer using scatterlist. + * @sg: scatterlist holding DMA buffers. + * @nents: number of scatterlist entries. + * @dir: one of possible dma_data_direction values. + * + * Depending on @direction, KMSAN: + * * checks the buffers in the scatterlist, if they are copied to device; + * * initializes the buffers, if they are copied from device; + * * does both, if this is a DMA_BIDIRECTIONAL transfer. + */ +void kmsan_handle_dma_sg(struct scatterlist *sg, int nents, + enum dma_data_direction dir); + #else static inline void kmsan_init_shadow(void) @@ -254,6 +285,16 @@ static inline void kmsan_iounmap_page_range(unsigned long start, { } +static inline void kmsan_handle_dma(struct page *page, size_t offset, + size_t size, enum dma_data_direction dir) +{ +} + +static inline void kmsan_handle_dma_sg(struct scatterlist *sg, int nents, + enum dma_data_direction dir) +{ +} + #endif #endif /* _LINUX_KMSAN_H */ diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c index 27f272381cf27..33437d6206445 100644 --- a/kernel/dma/mapping.c +++ b/kernel/dma/mapping.c @@ -10,6 +10,7 @@ #include <linux/dma-map-ops.h> #include <linux/export.h> #include <linux/gfp.h> +#include <linux/kmsan.h> #include <linux/of_device.h> #include <linux/slab.h> #include <linux/vmalloc.h> @@ -156,6 +157,7 @@ dma_addr_t dma_map_page_attrs(struct device *dev, struct page *page, addr = dma_direct_map_page(dev, page, offset, size, dir, attrs); else addr = ops->map_page(dev, page, offset, size, dir, attrs); + kmsan_handle_dma(page, offset, size, dir); debug_dma_map_page(dev, page, offset, size, dir, addr, attrs); return addr; @@ -194,11 +196,13 @@ static int __dma_map_sg_attrs(struct device *dev, struct scatterlist *sg, else ents = ops->map_sg(dev, sg, nents, dir, attrs); - if (ents > 0) + if (ents > 0) { + kmsan_handle_dma_sg(sg, nents, dir); debug_dma_map_sg(dev, sg, nents, ents, dir, attrs); - else if (WARN_ON_ONCE(ents != -EINVAL && ents != -ENOMEM && - ents != -EIO && ents != -EREMOTEIO)) + } else if (WARN_ON_ONCE(ents != -EINVAL && ents != -ENOMEM && + ents != -EIO && ents != -EREMOTEIO)) { return -EIO; + } return ents; } diff --git a/mm/kmsan/hooks.c b/mm/kmsan/hooks.c index 5c0eb25d984d7..563c09443a37a 100644 --- a/mm/kmsan/hooks.c +++ b/mm/kmsan/hooks.c @@ -10,10 +10,12 @@ */ #include <linux/cacheflush.h> +#include <linux/dma-direction.h> #include <linux/gfp.h> #include <linux/kmsan.h> #include <linux/mm.h> #include <linux/mm_types.h> +#include <linux/scatterlist.h> #include <linux/slab.h> #include <linux/uaccess.h> @@ -243,6 +245,63 @@ void kmsan_copy_to_user(void __user *to, const void *from, size_t to_copy, } EXPORT_SYMBOL(kmsan_copy_to_user); +static void kmsan_handle_dma_page(const void *addr, size_t size, + enum dma_data_direction dir) +{ + switch (dir) { + case DMA_BIDIRECTIONAL: + kmsan_internal_check_memory((void *)addr, size, /*user_addr*/ 0, + REASON_ANY); + kmsan_internal_unpoison_memory((void *)addr, size, + /*checked*/ false); + break; + case DMA_TO_DEVICE: + kmsan_internal_check_memory((void *)addr, size, /*user_addr*/ 0, + REASON_ANY); + break; + case DMA_FROM_DEVICE: + kmsan_internal_unpoison_memory((void *)addr, size, + /*checked*/ false); + break; + case DMA_NONE: + break; + } +} + +/* Helper function to handle DMA data transfers. */ +void kmsan_handle_dma(struct page *page, size_t offset, size_t size, + enum dma_data_direction dir) +{ + u64 page_offset, to_go, addr; + + if (PageHighMem(page)) + return; + addr = (u64)page_address(page) + offset; + /* + * The kernel may occasionally give us adjacent DMA pages not belonging + * to the same allocation. Process them separately to avoid triggering + * internal KMSAN checks. + */ + while (size > 0) { + page_offset = addr % PAGE_SIZE; + to_go = min(PAGE_SIZE - page_offset, (u64)size); + kmsan_handle_dma_page((void *)addr, to_go, dir); + addr += to_go; + size -= to_go; + } +} + +void kmsan_handle_dma_sg(struct scatterlist *sg, int nents, + enum dma_data_direction dir) +{ + struct scatterlist *item; + int i; + + for_each_sg(sg, item, nents, i) + kmsan_handle_dma(sg_page(item), item->offset, item->length, + dir); +} + /* Functions from kmsan-checks.h follow. */ void kmsan_poison_memory(const void *address, size_t size, gfp_t flags) { -- 2.37.2.789.g6183377224-goog
