From e873c74132f0c5f1452816cd9bb26208f0bba1e1 Mon Sep 17 00:00:00 2001 From: Shivank Garg Date: Sat, 22 Aug 2026 19:22:05 +0000 Subject: dmaengine: fix use-after-free in dma_chan_put() and dma_release_channel() When dma_device_put() drops the last reference on chan->device->ref, dma_device_release() runs and may free the dma_device along with its channels. dma_chan_put() then still reads chan->device->owner via dma_chan_to_owner() for the trailing module_put(). KASAN catches it: slab-use-after-free in dma_chan_put+0x3e6/0x4c0 Read of size 8 by task insmod/6319 Freed by task 6319: kfree+0x225/0x470 dma_chan_put+0x395/0x4c0 dmaengine_put+0xf8/0x160 Cache the module owner in dma_chan_put() before the put so the trailing module_put() does not need chan->device. Fixes: 8ad342a86359 ("dmaengine: Add reference counting to dma_device struct") Suggested-by: Sashiko Link: https://sashiko.dev/#/patchset/20260518-dmaengine-kref-fix-v1-1-4d6125048fb7@amd.com Reviewed-by: Frank Li Reviewed-by: Logan Gunthorpe Signed-off-by: Shivank Garg Link: https://patch.msgid.link/20260822-dmaengine-kref-fix-v5-3-d4a4ee47d927@amd.com Signed-off-by: Vinod Koul --- include/asm-generic/bitops/sched.h | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) create mode 100644 include/asm-generic/bitops/sched.h (limited to 'include/asm-generic/bitops/sched.h') diff --git a/include/asm-generic/bitops/sched.h b/include/asm-generic/bitops/sched.h new file mode 100644 index 000000000..86470cfce --- /dev/null +++ b/include/asm-generic/bitops/sched.h @@ -0,0 +1,32 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_GENERIC_BITOPS_SCHED_H_ +#define _ASM_GENERIC_BITOPS_SCHED_H_ + +#include /* unlikely() */ +#include + +/* + * Every architecture must define this function. It's the fastest + * way of searching a 100-bit bitmap. It's guaranteed that at least + * one of the 100 bits is cleared. + */ +static inline int sched_find_first_bit(const unsigned long *b) +{ +#if BITS_PER_LONG == 64 + if (b[0]) + return __ffs(b[0]); + return __ffs(b[1]) + 64; +#elif BITS_PER_LONG == 32 + if (b[0]) + return __ffs(b[0]); + if (b[1]) + return __ffs(b[1]) + 32; + if (b[2]) + return __ffs(b[2]) + 64; + return __ffs(b[3]) + 96; +#else +#error BITS_PER_LONG not defined +#endif +} + +#endif /* _ASM_GENERIC_BITOPS_SCHED_H_ */ -- cgit v1.3.1