Messages in this thread | | | Subject | Re: [PATCH] bpf: explicitly memset the bpf_attr structure | From | Yonghong Song <> | Date | Fri, 20 Mar 2020 08:31:03 -0700 |
| |
On 3/20/20 8:24 AM, Daniel Borkmann wrote: > On 3/20/20 10:48 AM, Greg Kroah-Hartman wrote: >> For the bpf syscall, we are relying on the compiler to properly zero out >> the bpf_attr union that we copy userspace data into. Unfortunately that >> doesn't always work properly, padding and other oddities might not be >> correctly zeroed, and in some tests odd things have been found when the >> stack is pre-initialized to other values. >> >> Fix this by explicitly memsetting the structure to 0 before using it. >> >> Reported-by: Maciej Żenczykowski <maze@google.com> >> Reported-by: John Stultz <john.stultz@linaro.org> >> Reported-by: Alexander Potapenko <glider@google.com> >> Reported-by: Alistair Delva <adelva@google.com> >> Cc: stable <stable@vger.kernel.org> >> Link: >> https://urldefense.proofpoint.com/v2/url?u=https-3A__android-2Dreview.googlesource.com_c_kernel_common_-2B_1235490&d=DwIDaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=DA8e1B5r073vIqRrFz7MRA&m=Fz_Xc6psG64uMowK2qpH0gTLj0NQE7k1CTWb5fODVeg&s=WKW0vq8WBALfwsSq5xGGWwxuLWKfI0DNN9XVMc1DkcE&e= >> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> >> --- >> kernel/bpf/syscall.c | 3 ++- >> 1 file changed, 2 insertions(+), 1 deletion(-) >> >> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c >> index a91ad518c050..a4b1de8ea409 100644 >> --- a/kernel/bpf/syscall.c >> +++ b/kernel/bpf/syscall.c >> @@ -3354,7 +3354,7 @@ static int bpf_map_do_batch(const union bpf_attr >> *attr, >> SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, >> unsigned int, size) >> { >> - union bpf_attr attr = {}; >> + union bpf_attr attr; >> int err; >> if (sysctl_unprivileged_bpf_disabled && !capable(CAP_SYS_ADMIN)) >> @@ -3366,6 +3366,7 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr >> __user *, uattr, unsigned int, siz >> size = min_t(u32, size, sizeof(attr)); >> /* copy attributes from user space, may be less than >> sizeof(bpf_attr) */ >> + memset(&attr, 0, sizeof(attr)); > > Thanks for the fix, there are a few more of these places. We would also > need > to cover: > > - bpf_prog_get_info_by_fd() > - bpf_map_get_info_by_fd() > - btf_get_info_by_fd()
Not sure whether in these places existing approach will cause kernel failure or not. They did not call CHECK_ATTR, e.g., for bpf_prog_info structure.
> > Please add these as well to your fix. > >> if (copy_from_user(&attr, uattr, size) != 0) >> return -EFAULT; >> >> base-commit: 6c90b86a745a446717fdf408c4a8a4631a5e8ee3 >> >
| |