I have tested that patches 2 and 3 work using the following reproducers. I did not write a reproducer for the issue described in patch 1.
Reproducer for F_SEAL_FUTURE_WRITE not being respected: ``` #define _GNU_SOURCE #include <err.h> #include <fcntl.h> #include <stdio.h> #include <unistd.h> #include <sys/ioctl.h> #include <sys/mman.h> #include <linux/udmabuf.h>
#define SYSCHK(x) ({ \ typeof(x) __res = (x); \ if (__res == (typeof(x))-1) \ err(1, "SYSCHK(" #x ")"); \ __res; \ })
int main(void) { int memfd = SYSCHK(memfd_create("test", MFD_ALLOW_SEALING)); SYSCHK(ftruncate(memfd, 0x1000)); SYSCHK(fcntl(memfd, F_ADD_SEALS, F_SEAL_SHRINK|F_SEAL_FUTURE_WRITE)); int udmabuf_fd = SYSCHK(open("/dev/udmabuf", O_RDWR)); struct udmabuf_create create_arg = { .memfd = memfd, .flags = 0, .offset = 0, .size = 0x1000 }; int buf_fd = SYSCHK(ioctl(udmabuf_fd, UDMABUF_CREATE, &create_arg)); printf("created udmabuf buffer fd %d\n", buf_fd); char *map = SYSCHK(mmap(NULL, 0x1000, PROT_READ|PROT_WRITE, MAP_SHARED, buf_fd, 0)); *map = 'a'; } ```
Reproducer for the memory leak (if you run this for a while, your memory usage will steadily go up, and /sys/kernel/debug/dma_buf/bufinfo will contain a ton of entries): ``` #define _GNU_SOURCE #include <err.h> #include <errno.h> #include <assert.h> #include <fcntl.h> #include <stdio.h> #include <unistd.h> #include <sys/ioctl.h> #include <sys/mman.h> #include <sys/resource.h> #include <linux/udmabuf.h>
#define SYSCHK(x) ({ \ typeof(x) __res = (x); \ if (__res == (typeof(x))-1) \ err(1, "SYSCHK(" #x ")"); \ __res; \ })
int main(void) { int memfd = SYSCHK(memfd_create("test", MFD_ALLOW_SEALING)); SYSCHK(ftruncate(memfd, 0x1000)); SYSCHK(fcntl(memfd, F_ADD_SEALS, F_SEAL_SHRINK)); int udmabuf_fd = SYSCHK(open("/dev/udmabuf", O_RDWR));
// prevent creating new FDs struct rlimit rlim = { .rlim_cur = 1, .rlim_max = 1 }; SYSCHK(setrlimit(RLIMIT_NOFILE, &rlim));
while (1) { struct udmabuf_create create_arg = { .memfd = memfd, .flags = 0, .offset = 0, .size = 0x1000 }; int buf_fd = ioctl(udmabuf_fd, UDMABUF_CREATE, &create_arg); assert(buf_fd == -1); assert(errno == EMFILE); } } ```
Signed-off-by: Jann Horn jannh@google.com --- Jann Horn (3): udmabuf: fix racy memfd sealing check udmabuf: also check for F_SEAL_FUTURE_WRITE udmabuf: fix memory leak on last export_udmabuf() error path
drivers/dma-buf/udmabuf.c | 36 ++++++++++++++++++++---------------- 1 file changed, 20 insertions(+), 16 deletions(-) --- base-commit: b86545e02e8c22fb89218f29d381fa8e8b91d815 change-id: 20241203-udmabuf-fixes-d0435ebab663