The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-4.19.y git checkout FETCH_HEAD git cherry-pick -x fd7276189450110ed835eb0a334e62d2f1c4e3be # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2023040304-splashed-consult-3a39@gregkh' --subject-prefix 'PATCH 4.19.y' HEAD^..

Possible dependencies:

fd7276189450 ("powerpc: Don't try to copy PPR for task with NULL pt_regs") 47e12855a91d ("powerpc: switch to ->regset_get()") 6e0b79750ce2 ("powerpc/ptrace: move register viewing functions out of ptrace.c") 7c1f8db019f8 ("powerpc/ptrace: split out TRANSACTIONAL_MEM related functions.") 60ef9dbd9d2a ("powerpc/ptrace: split out SPE related functions.") 1b20773b00b7 ("powerpc/ptrace: split out ALTIVEC related functions.") 7b99ed4e8e3a ("powerpc/ptrace: split out VSX related functions.") 963ae6b2ff1c ("powerpc/ptrace: drop PARAMETER_SAVE_AREA_OFFSET") f1763e623c69 ("powerpc/ptrace: drop unnecessary #ifdefs CONFIG_PPC64") b3138536c837 ("powerpc/ptrace: remove unused header includes") da9a1c10e2c7 ("powerpc: Move ptrace into a subdirectory.") 68b34588e202 ("powerpc/64/sycall: Implement syscall entry/exit logic in C") 965dd3ad3076 ("powerpc/64/syscall: Remove non-volatile GPR save optimisation") fddb5d430ad9 ("open: introduce openat2(2) syscall") 793b08e2efff ("powerpc/kexec: Move kexec files into a dedicated subdir.") 9f7bd9201521 ("powerpc/32: Split kexec low level code out of misc_32.S") b020aa9d1e87 ("powerpc: cleanup hw_irq.h") 0671c5b84e9e ("MIPS: Wire up clone3 syscall") 45824fc0da6e ("Merge tag 'powerpc-5.4-1' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From fd7276189450110ed835eb0a334e62d2f1c4e3be Mon Sep 17 00:00:00 2001 From: Jens Axboe axboe@kernel.dk Date: Sun, 26 Mar 2023 16:15:57 -0600 Subject: [PATCH] powerpc: Don't try to copy PPR for task with NULL pt_regs

powerpc sets up PF_KTHREAD and PF_IO_WORKER with a NULL pt_regs, which from my (arguably very short) checking is not commonly done for other archs. This is fine, except when PF_IO_WORKER's have been created and the task does something that causes a coredump to be generated. Then we get this crash:

Kernel attempted to read user page (160) - exploit attempt? (uid: 1000) BUG: Kernel NULL pointer dereference on read at 0x00000160 Faulting instruction address: 0xc0000000000c3a60 Oops: Kernel access of bad area, sig: 11 [#1] LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=32 NUMA pSeries Modules linked in: bochs drm_vram_helper drm_kms_helper xts binfmt_misc ecb ctr syscopyarea sysfillrect cbc sysimgblt drm_ttm_helper aes_generic ttm sg libaes evdev joydev virtio_balloon vmx_crypto gf128mul drm dm_mod fuse loop configfs drm_panel_orientation_quirks ip_tables x_tables autofs4 hid_generic usbhid hid xhci_pci xhci_hcd usbcore usb_common sd_mod CPU: 1 PID: 1982 Comm: ppc-crash Not tainted 6.3.0-rc2+ #88 Hardware name: IBM pSeries (emulated by qemu) POWER9 (raw) 0x4e1202 0xf000005 of:SLOF,HEAD hv:linux,kvm pSeries NIP: c0000000000c3a60 LR: c000000000039944 CTR: c0000000000398e0 REGS: c0000000041833b0 TRAP: 0300 Not tainted (6.3.0-rc2+) MSR: 800000000280b033 <SF,VEC,VSX,EE,FP,ME,IR,DR,RI,LE> CR: 88082828 XER: 200400f8 ... NIP memcpy_power7+0x200/0x7d0 LR ppr_get+0x64/0xb0 Call Trace: ppr_get+0x40/0xb0 (unreliable) __regset_get+0x180/0x1f0 regset_get_alloc+0x64/0x90 elf_core_dump+0xb98/0x1b60 do_coredump+0x1c34/0x24a0 get_signal+0x71c/0x1410 do_notify_resume+0x140/0x6f0 interrupt_exit_user_prepare_main+0x29c/0x320 interrupt_exit_user_prepare+0x6c/0xa0 interrupt_return_srr_user+0x8/0x138

Because ppr_get() is trying to copy from a PF_IO_WORKER with a NULL pt_regs.

Check for a valid pt_regs in both ppc_get/ppr_set, and return an error if not set. The actual error value doesn't seem to be important here, so just pick -EINVAL.

Fixes: fa439810cc1b ("powerpc/ptrace: Enable support for NT_PPPC_TAR, NT_PPC_PPR, NT_PPC_DSCR") Cc: stable@vger.kernel.org # v4.8+ Signed-off-by: Jens Axboe axboe@kernel.dk [mpe: Trim oops in change log, add Fixes & Cc stable] Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://msgid.link/d9f63344-fe7c-56ae-b420-4a1a04a2ae4c@kernel.dk

diff --git a/arch/powerpc/kernel/ptrace/ptrace-view.c b/arch/powerpc/kernel/ptrace/ptrace-view.c index 2087a785f05f..5fff0d04b23f 100644 --- a/arch/powerpc/kernel/ptrace/ptrace-view.c +++ b/arch/powerpc/kernel/ptrace/ptrace-view.c @@ -290,6 +290,9 @@ static int gpr_set(struct task_struct *target, const struct user_regset *regset, static int ppr_get(struct task_struct *target, const struct user_regset *regset, struct membuf to) { + if (!target->thread.regs) + return -EINVAL; + return membuf_write(&to, &target->thread.regs->ppr, sizeof(u64)); }

@@ -297,6 +300,9 @@ static int ppr_set(struct task_struct *target, const struct user_regset *regset, unsigned int pos, unsigned int count, const void *kbuf, const void __user *ubuf) { + if (!target->thread.regs) + return -EINVAL; + return user_regset_copyin(&pos, &count, &kbuf, &ubuf, &target->thread.regs->ppr, 0, sizeof(u64)); }