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/local.h | 57 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 57 insertions(+) create mode 100644 include/asm-generic/local.h (limited to 'include/asm-generic/local.h') diff --git a/include/asm-generic/local.h b/include/asm-generic/local.h new file mode 100644 index 000000000..7f97018df --- /dev/null +++ b/include/asm-generic/local.h @@ -0,0 +1,57 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_GENERIC_LOCAL_H +#define _ASM_GENERIC_LOCAL_H + +#include +#include +#include + +/* + * A signed long type for operations which are atomic for a single CPU. + * Usually used in combination with per-cpu variables. + * + * This is the default implementation, which uses atomic_long_t. Which is + * rather pointless. The whole point behind local_t is that some processors + * can perform atomic adds and subtracts in a manner which is atomic wrt IRQs + * running on this CPU. local_t allows exploitation of such capabilities. + */ + +/* Implement in terms of atomics. */ + +/* Don't use typedef: don't want them to be mixed with atomic_t's. */ +typedef struct +{ + atomic_long_t a; +} local_t; + +#define LOCAL_INIT(i) { ATOMIC_LONG_INIT(i) } + +#define local_read(l) atomic_long_read(&(l)->a) +#define local_set(l,i) atomic_long_set((&(l)->a),(i)) +#define local_inc(l) atomic_long_inc(&(l)->a) +#define local_dec(l) atomic_long_dec(&(l)->a) +#define local_add(i,l) atomic_long_add((i),(&(l)->a)) +#define local_sub(i,l) atomic_long_sub((i),(&(l)->a)) + +#define local_sub_and_test(i, l) atomic_long_sub_and_test((i), (&(l)->a)) +#define local_dec_and_test(l) atomic_long_dec_and_test(&(l)->a) +#define local_inc_and_test(l) atomic_long_inc_and_test(&(l)->a) +#define local_add_negative(i, l) atomic_long_add_negative((i), (&(l)->a)) +#define local_add_return(i, l) atomic_long_add_return((i), (&(l)->a)) +#define local_sub_return(i, l) atomic_long_sub_return((i), (&(l)->a)) +#define local_inc_return(l) atomic_long_inc_return(&(l)->a) + +#define local_cmpxchg(l, o, n) atomic_long_cmpxchg((&(l)->a), (o), (n)) +#define local_try_cmpxchg(l, po, n) atomic_long_try_cmpxchg((&(l)->a), (po), (n)) +#define local_xchg(l, n) atomic_long_xchg((&(l)->a), (n)) +#define local_add_unless(l, _a, u) atomic_long_add_unless((&(l)->a), (_a), (u)) +#define local_inc_not_zero(l) atomic_long_inc_not_zero(&(l)->a) + +/* Non-atomic variants, ie. preemption disabled and won't be touched + * in interrupt, etc. Some archs can optimize this case well. */ +#define __local_inc(l) local_set((l), local_read(l) + 1) +#define __local_dec(l) local_set((l), local_read(l) - 1) +#define __local_add(i,l) local_set((l), local_read(l) + (i)) +#define __local_sub(i,l) local_set((l), local_read(l) - (i)) + +#endif /* _ASM_GENERIC_LOCAL_H */ -- cgit v1.3.1