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 --- samples/bpf/tracex4_user.c | 96 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 96 insertions(+) create mode 100644 samples/bpf/tracex4_user.c (limited to 'samples/bpf/tracex4_user.c') diff --git a/samples/bpf/tracex4_user.c b/samples/bpf/tracex4_user.c new file mode 100644 index 000000000..a5145ad72 --- /dev/null +++ b/samples/bpf/tracex4_user.c @@ -0,0 +1,96 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* Copyright (c) 2015 PLUMgrid, http://plumgrid.com + */ +#include +#include +#include +#include +#include +#include +#include + +#include +#include + +struct pair { + long long val; + __u64 ip; +}; + +static __u64 time_get_ns(void) +{ + struct timespec ts; + + clock_gettime(CLOCK_MONOTONIC, &ts); + return ts.tv_sec * 1000000000ull + ts.tv_nsec; +} + +static void print_old_objects(int fd) +{ + long long val = time_get_ns(); + __u64 key, next_key; + struct pair v; + + key = write(1, "\e[1;1H\e[2J", 11); /* clear screen */ + + key = -1; + while (bpf_map_get_next_key(fd, &key, &next_key) == 0) { + bpf_map_lookup_elem(fd, &next_key, &v); + key = next_key; + if (val - v.val < 1000000000ll) + /* object was allocated more then 1 sec ago */ + continue; + printf("obj 0x%llx is %2lldsec old was allocated at ip %llx\n", + next_key, (val - v.val) / 1000000000ll, v.ip); + } +} + +int main(int ac, char **argv) +{ + struct bpf_link *links[2]; + struct bpf_program *prog; + struct bpf_object *obj; + char filename[256]; + int map_fd, j = 0; + + snprintf(filename, sizeof(filename), "%s.bpf.o", argv[0]); + obj = bpf_object__open_file(filename, NULL); + if (libbpf_get_error(obj)) { + fprintf(stderr, "ERROR: opening BPF object file failed\n"); + return 0; + } + + /* load BPF program */ + if (bpf_object__load(obj)) { + fprintf(stderr, "ERROR: loading BPF object file failed\n"); + goto cleanup; + } + + map_fd = bpf_object__find_map_fd_by_name(obj, "my_map"); + if (map_fd < 0) { + fprintf(stderr, "ERROR: finding a map in obj file failed\n"); + goto cleanup; + } + + bpf_object__for_each_program(prog, obj) { + links[j] = bpf_program__attach(prog); + if (libbpf_get_error(links[j])) { + fprintf(stderr, "ERROR: bpf_program__attach failed\n"); + links[j] = NULL; + goto cleanup; + } + j++; + } + + while (1) { + print_old_objects(map_fd); + sleep(1); + } + +cleanup: + for (j--; j >= 0; j--) + bpf_link__destroy(links[j]); + + bpf_object__close(obj); + return 0; +} -- cgit v1.3.1