Messages in this thread Patch in this message | | | From | Arnd Bergmann <> | Subject | [PATCH] ARM: dma-mapping: fix out of bounds access in CMA | Date | Tue, 23 Mar 2021 14:14:13 +0100 |
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From: Arnd Bergmann <arnd@arndb.de>
Dereferencing a zero-length array is always a bug, and we get a warning with 'make W=1' here:
arch/arm/mm/dma-mapping.c: In function 'dma_contiguous_early_fixup': arch/arm/mm/dma-mapping.c:395:15: error: array subscript <unknown> is outside array bounds of 'struct dma_contig_early_reserve[0]' [-Werror=array-bounds] 395 | dma_mmu_remap[dma_mmu_remap_num].base = base; | ~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~ arch/arm/mm/dma-mapping.c:389:40: note: while referencing 'dma_mmu_remap' 389 | static struct dma_contig_early_reserve dma_mmu_remap[MAX_CMA_AREAS] __initdata; | ^~~~~~~~~~~~~ arch/arm/mm/dma-mapping.c:396:15: error: array subscript <unknown> is outside array bounds of 'struct dma_contig_early_reserve[0]' [-Werror=array-bounds]
Add a runtime check to prevent this from happening, while also avoiding the compile-time warning.
Fixes: c79095092834 ("ARM: integrate CMA with DMA-mapping subsystem") Signed-off-by: Arnd Bergmann <arnd@arndb.de> --- arch/arm/mm/dma-mapping.c | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c index c4b8df2ad328..af29344fb150 100644 --- a/arch/arm/mm/dma-mapping.c +++ b/arch/arm/mm/dma-mapping.c @@ -392,6 +392,11 @@ static int dma_mmu_remap_num __initdata; void __init dma_contiguous_early_fixup(phys_addr_t base, unsigned long size) { + if (!MAX_CMA_AREAS || dma_mmu_remap_num >= MAX_CMA_AREAS) { + WARN_ONCE(1, "number of CMA areas\n"); + return; + } + dma_mmu_remap[dma_mmu_remap_num].base = base; dma_mmu_remap[dma_mmu_remap_num].size = size; dma_mmu_remap_num++; @@ -400,6 +405,10 @@ void __init dma_contiguous_early_fixup(phys_addr_t base, unsigned long size) void __init dma_contiguous_remap(void) { int i; + + if (!MAX_CMA_AREAS) + return; + for (i = 0; i < dma_mmu_remap_num; i++) { phys_addr_t start = dma_mmu_remap[i].base; phys_addr_t end = start + dma_mmu_remap[i].size; -- 2.29.2
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