# git rev-parse -q --verify 6865920b3f27b31bb9280088f3a837fd2090a327^{commit} 6865920b3f27b31bb9280088f3a837fd2090a327 already have revision, skipping fetch # git checkout -q -f -B kisskb 6865920b3f27b31bb9280088f3a837fd2090a327 # git clean -qxdf # < git log -1 # commit 6865920b3f27b31bb9280088f3a837fd2090a327 # Author: Michael Ellerman # Date: Tue Oct 10 22:47:50 2023 +1100 # # powerpc/47x: Fix 47x syscall return crash # # Eddie reported that newer kernels were crashing during boot on his 476 # FSP2 system: # # kernel tried to execute user page (b7ee2000) - exploit attempt? (uid: 0) # BUG: Unable to handle kernel instruction fetch # Faulting instruction address: 0xb7ee2000 # Oops: Kernel access of bad area, sig: 11 [#1] # BE PAGE_SIZE=4K FSP-2 # Modules linked in: # CPU: 0 PID: 61 Comm: mount Not tainted 6.1.55-d23900f.ppcnf-fsp2 #1 # Hardware name: ibm,fsp2 476fpe 0x7ff520c0 FSP-2 # NIP:  b7ee2000 LR: 8c008000 CTR: 00000000 # REGS: bffebd83 TRAP: 0400   Not tainted (6.1.55-d23900f.ppcnf-fs p2) # MSR:  00000030   CR: 00001000  XER: 20000000 # GPR00: c00110ac bffebe63 bffebe7e bffebe88 8c008000 00001000 00000d12 b7ee2000 # GPR08: 00000033 00000000 00000000 c139df10 48224824 1016c314 10160000 00000000 # GPR16: 10160000 10160000 00000008 00000000 10160000 00000000 10160000 1017f5b0 # GPR24: 1017fa50 1017f4f0 1017fa50 1017f740 1017f630 00000000 00000000 1017f4f0 # NIP [b7ee2000] 0xb7ee2000 # LR [8c008000] 0x8c008000 # Call Trace: # Instruction dump: # XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX # XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX # ---[ end trace 0000000000000000 ]--- # # The problem is in ret_from_syscall where the check for # icache_44x_need_flush is done. When the flush is needed the code jumps # out-of-line to do the flush, and then intends to jump back to continue # the syscall return. # # However the branch back to label 1b doesn't return to the correct # location, instead branching back just prior to the return to userspace, # causing bogus register values to be used by the rfi. # # The breakage was introduced by commit 6f76a01173cc # ("powerpc/syscall: implement system call entry/exit logic in C for PPC32") which # inadvertently removed the "1" label and reused it elsewhere. # # Fix it by adding named local labels in the correct locations. Note that # the return label needs to be outside the ifdef so that CONFIG_PPC_47x=n # compiles. # # Fixes: 6f76a01173cc ("powerpc/syscall: implement system call entry/exit logic in C for PPC32") # Cc: stable@vger.kernel.org # v5.12+ # Reported-by: Eddie James # Tested-by: Eddie James # Link: https://lore.kernel.org/linuxppc-dev/fdaadc46-7476-9237-e104-1d2168526e72@linux.ibm.com/ # Signed-off-by: Michael Ellerman # Link: https://msgid.link/20231010114750.847794-1-mpe@ellerman.id.au # < /opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-gcc --version # < /opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-ld --version # < git log --format=%s --max-count=1 6865920b3f27b31bb9280088f3a837fd2090a327 # make -s -j 32 ARCH=powerpc O=/kisskb/build/powerpc-fixes_pseries_defconfig+NO_MEMORY_HOTPLUG_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux- pseries_defconfig Using /kisskb/src/arch/powerpc/configs/ppc64_defconfig as base Merging /kisskb/src/arch/powerpc/configs/le.config Merging /kisskb/src/arch/powerpc/configs/guest.config Value of CONFIG_VIRTIO_BLK is redefined by fragment /kisskb/src/arch/powerpc/configs/guest.config: Previous value: CONFIG_VIRTIO_BLK=m New value: CONFIG_VIRTIO_BLK=y Value of CONFIG_SCSI_VIRTIO is redefined by fragment /kisskb/src/arch/powerpc/configs/guest.config: Previous value: CONFIG_SCSI_VIRTIO=m New value: CONFIG_SCSI_VIRTIO=y Value of CONFIG_VIRTIO_NET is redefined by fragment /kisskb/src/arch/powerpc/configs/guest.config: Previous value: CONFIG_VIRTIO_NET=m New value: CONFIG_VIRTIO_NET=y Value of CONFIG_VIRTIO_CONSOLE is redefined by fragment /kisskb/src/arch/powerpc/configs/guest.config: Previous value: CONFIG_VIRTIO_CONSOLE=m New value: CONFIG_VIRTIO_CONSOLE=y Value of CONFIG_VIRTIO_PCI is redefined by fragment /kisskb/src/arch/powerpc/configs/guest.config: Previous value: CONFIG_VIRTIO_PCI=m New value: CONFIG_VIRTIO_PCI=y Value of CONFIG_VIRTIO_BALLOON is redefined by fragment /kisskb/src/arch/powerpc/configs/guest.config: Previous value: CONFIG_VIRTIO_BALLOON=m New value: CONFIG_VIRTIO_BALLOON=y Value of CONFIG_VHOST_NET is redefined by fragment /kisskb/src/arch/powerpc/configs/guest.config: Previous value: CONFIG_VHOST_NET=m New value: CONFIG_VHOST_NET=y Value of CONFIG_IBMVETH is redefined by fragment /kisskb/src/arch/powerpc/configs/guest.config: Previous value: CONFIG_IBMVETH=m New value: CONFIG_IBMVETH=y Value of CONFIG_IBMVNIC is redefined by fragment /kisskb/src/arch/powerpc/configs/guest.config: Previous value: CONFIG_IBMVNIC=m New value: CONFIG_IBMVNIC=y Merging /kisskb/src/arch/powerpc/configs/kvm_guest.config # # merged configuration written to .config (needs make) # # Added to kconfig CONFIG_MEMORY_HOTPLUG=n # Added to kconfig CONFIG_MEMORY_HOTREMOVE=n # < make -s -j 32 ARCH=powerpc O=/kisskb/build/powerpc-fixes_pseries_defconfig+NO_MEMORY_HOTPLUG_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux- help # make -s -j 32 ARCH=powerpc O=/kisskb/build/powerpc-fixes_pseries_defconfig+NO_MEMORY_HOTPLUG_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux- olddefconfig # make -s -j 32 ARCH=powerpc O=/kisskb/build/powerpc-fixes_pseries_defconfig+NO_MEMORY_HOTPLUG_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux- Completed OK # rm -rf /kisskb/build/powerpc-fixes_pseries_defconfig+NO_MEMORY_HOTPLUG_powerpc-gcc5 # Build took: 0:02:48.473311