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/seccomp/dropper.c | 77 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 77 insertions(+) create mode 100644 samples/seccomp/dropper.c (limited to 'samples/seccomp/dropper.c') diff --git a/samples/seccomp/dropper.c b/samples/seccomp/dropper.c new file mode 100644 index 000000000..4bca4b70f --- /dev/null +++ b/samples/seccomp/dropper.c @@ -0,0 +1,77 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Naive system call dropper built on seccomp_filter. + * + * Copyright (c) 2012 The Chromium OS Authors + * Author: Will Drewry + * + * The code may be used by anyone for any purpose, + * and can serve as a starting point for developing + * applications using prctl(PR_SET_SECCOMP, 2, ...). + * + * When run, returns the specified errno for the specified + * system call number against the given architecture. + * + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +static int install_filter(int arch, int nr, int error) +{ + struct sock_filter filter[] = { + BPF_STMT(BPF_LD+BPF_W+BPF_ABS, + (offsetof(struct seccomp_data, arch))), + BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, arch, 0, 3), + BPF_STMT(BPF_LD+BPF_W+BPF_ABS, + (offsetof(struct seccomp_data, nr))), + BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, nr, 0, 1), + BPF_STMT(BPF_RET+BPF_K, + SECCOMP_RET_ERRNO|(error & SECCOMP_RET_DATA)), + BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW), + }; + struct sock_fprog prog = { + .len = (unsigned short)(sizeof(filter)/sizeof(filter[0])), + .filter = filter, + }; + if (error == -1) { + struct sock_filter kill = BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_KILL); + filter[4] = kill; + } + if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) { + perror("prctl(NO_NEW_PRIVS)"); + return 1; + } + if (prctl(PR_SET_SECCOMP, 2, &prog)) { + perror("prctl(PR_SET_SECCOMP)"); + return 1; + } + return 0; +} + +int main(int argc, char **argv) +{ + if (argc < 5) { + fprintf(stderr, "Usage:\n" + "dropper []\n" + "Hint: AUDIT_ARCH_I386: 0x%X\n" + " AUDIT_ARCH_X86_64: 0x%X\n" + " errno == -1 means SECCOMP_RET_KILL\n" + "\n", AUDIT_ARCH_I386, AUDIT_ARCH_X86_64); + return 1; + } + if (install_filter(strtol(argv[1], NULL, 0), strtol(argv[2], NULL, 0), + strtol(argv[3], NULL, 0))) + return 1; + execv(argv[4], &argv[4]); + printf("Failed to execv\n"); + return 255; +} -- cgit v1.3.1