On Thu, Jul 17, 2025 at 4:40 PM Paolo Abeni <pabeni@xxxxxxxxxx> wrote: > > On 7/15/25 10:11 AM, Pranav Tyagi wrote: > > A NULL page from sg_page() in sk_msg_recvmsg() can reach > > __kmap_local_page_prot() and crash the kernel. Add a check for the page > > before calling copy_page_to_iter() and fail early with -EFAULT to > > prevent the crash. > > Interesting. I thought the sge in this case are build from the kernel, I > did not expect a null page to be possible. Can you describe in the > commit message how such bad sges are created? > > > > > Reported-by: syzbot+b18872ea9631b5dcef3b@xxxxxxxxxxxxxxxxxxxxxxxxx > > Closes: https://syzkaller.appspot.com/bug?extid=b18872ea9631b5dcef3b > > Fixes: 2bc793e3272a ("skmsg: Extract __tcp_bpf_recvmsg() and tcp_bpf_wait_data()") > > Signed-off-by: Pranav Tyagi <pranav.tyagi03@xxxxxxxxx> > > Does not apply to net. Please rebase and resend, adding the target tree > in the subj prefix and specifying a revision number. > > Thanks, > > Paolo > > Hi Paolo, Apologies for a delayed response. I will send a v2 of the patch with all the required changes shortly. Also, as I am a beginner at kernel work, my initial intention was to just fix the bug and (honestly) I did not think about the cause of bad sges. But, I will definitely take a deep dive and try my level best to look for a suitable explanation for the same. Thanks for the feedback. Regards Pranav Tyagi
