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/binderfs/.gitignore | 2 + samples/binderfs/Makefile | 4 ++ samples/binderfs/binderfs_example.c | 82 +++++++++++++++++++++++++++++++++++++ 3 files changed, 88 insertions(+) create mode 100644 samples/binderfs/.gitignore create mode 100644 samples/binderfs/Makefile create mode 100644 samples/binderfs/binderfs_example.c (limited to 'samples/binderfs') diff --git a/samples/binderfs/.gitignore b/samples/binderfs/.gitignore new file mode 100644 index 000000000..8fa415a36 --- /dev/null +++ b/samples/binderfs/.gitignore @@ -0,0 +1,2 @@ +# SPDX-License-Identifier: GPL-2.0 +/binderfs_example diff --git a/samples/binderfs/Makefile b/samples/binderfs/Makefile new file mode 100644 index 000000000..629e43b9b --- /dev/null +++ b/samples/binderfs/Makefile @@ -0,0 +1,4 @@ +# SPDX-License-Identifier: GPL-2.0-only +userprogs-always-y += binderfs_example + +userccflags += -I usr/include diff --git a/samples/binderfs/binderfs_example.c b/samples/binderfs/binderfs_example.c new file mode 100644 index 000000000..0fd92cdda --- /dev/null +++ b/samples/binderfs/binderfs_example.c @@ -0,0 +1,82 @@ +// SPDX-License-Identifier: GPL-2.0 + +#define _GNU_SOURCE +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +int main(int argc, char *argv[]) +{ + int fd, ret, saved_errno; + struct binderfs_device device = { 0 }; + + ret = unshare(CLONE_NEWNS); + if (ret < 0) { + fprintf(stderr, "%s - Failed to unshare mount namespace\n", + strerror(errno)); + exit(EXIT_FAILURE); + } + + ret = mount(NULL, "/", NULL, MS_REC | MS_PRIVATE, 0); + if (ret < 0) { + fprintf(stderr, "%s - Failed to mount / as private\n", + strerror(errno)); + exit(EXIT_FAILURE); + } + + ret = mkdir("/dev/binderfs", 0755); + if (ret < 0 && errno != EEXIST) { + fprintf(stderr, "%s - Failed to create binderfs mountpoint\n", + strerror(errno)); + exit(EXIT_FAILURE); + } + + ret = mount(NULL, "/dev/binderfs", "binder", 0, 0); + if (ret < 0) { + fprintf(stderr, "%s - Failed to mount binderfs\n", + strerror(errno)); + exit(EXIT_FAILURE); + } + + memcpy(device.name, "my-binder", strlen("my-binder")); + + fd = open("/dev/binderfs/binder-control", O_RDONLY | O_CLOEXEC); + if (fd < 0) { + fprintf(stderr, "%s - Failed to open binder-control device\n", + strerror(errno)); + exit(EXIT_FAILURE); + } + + ret = ioctl(fd, BINDER_CTL_ADD, &device); + saved_errno = errno; + close(fd); + errno = saved_errno; + if (ret < 0) { + fprintf(stderr, "%s - Failed to allocate new binder device\n", + strerror(errno)); + exit(EXIT_FAILURE); + } + + printf("Allocated new binder device with major %d, minor %d, and name %s\n", + device.major, device.minor, device.name); + + ret = unlink("/dev/binderfs/my-binder"); + if (ret < 0) { + fprintf(stderr, "%s - Failed to delete binder device\n", + strerror(errno)); + exit(EXIT_FAILURE); + } + + /* Cleanup happens when the mount namespace dies. */ + exit(EXIT_SUCCESS); +} -- cgit v1.3.1