# git rev-parse -q --verify a5a1fb260210893015872209514f73b55ab2138e^{commit} a5a1fb260210893015872209514f73b55ab2138e already have revision, skipping fetch # git checkout -q -f -B kisskb a5a1fb260210893015872209514f73b55ab2138e # git clean -qxdf # < git log -1 # commit a5a1fb260210893015872209514f73b55ab2138e # Author: Michael Ellerman # Date: Wed May 8 13:06:42 2019 +1000 # # powerpc/64s: Use early_mmu_has_feature() in set_kuap() # # When implementing the KUAP support on Radix we fixed one case where # mmu_has_feature() was being called too early in boot via # __put_user_size(). # # However since then some new code in linux-next has created a new path # via which we can end up calling mmu_has_feature() too early. # # On P9 this leads to crashes early in boot if we have both PPC_KUAP and # CONFIG_JUMP_LABEL_FEATURE_CHECK_DEBUG enabled. Our early boot code # calls printk() which calls probe_kernel_read(), that does a # __copy_from_user_inatomic() which calls into set_kuap() and that uses # mmu_has_feature(). # # At that point in boot we haven't patched MMU features yet so the debug # code in mmu_has_feature() complains, and calls printk(). At that point # we recurse, eg: # # ... # dump_stack+0xdc # probe_kernel_read+0x1a4 # check_pointer+0x58 # ... # printk+0x40 # dump_stack_print_info+0xbc # dump_stack+0x8 # probe_kernel_read+0x1a4 # probe_kernel_read+0x19c # check_pointer+0x58 # ... # printk+0x40 # cpufeatures_process_feature+0xc8 # scan_cpufeatures_subnodes+0x380 # of_scan_flat_dt_subnodes+0xb4 # dt_cpu_ftrs_scan_callback+0x158 # of_scan_flat_dt+0xf0 # dt_cpu_ftrs_scan+0x3c # early_init_devtree+0x360 # early_setup+0x9c # # And so on for infinity, symptom is a dead system. # # Even more fun is what happens when using the hash MMU (ie. p8 or p9 # with Radix disabled), and when we don't have # CONFIG_JUMP_LABEL_FEATURE_CHECK_DEBUG enabled. With the debug disabled # we don't check if static keys have been initialised, we just rely on # the jump label. But the jump label defaults to true so we just whack # the AMR even though Radix is not enabled. # # Clearing the AMR is fine, but after we've done the user copy we write # (0b11 << 62) into AMR. When using hash that makes all pages with key # zero no longer readable or writable. All kernel pages implicitly have # key zero, and so all of a sudden the kernel can't read or write any of # its memory. Again dead system. # # In the medium term we have several options for fixing this. # probe_kernel_read() doesn't need to touch AMR at all, it's not doing a # user access after all, but it uses __copy_from_user_inatomic() just # because it's easy, we could fix that. # # It would also be safe to default to not writing to the AMR during # early boot, until we've detected features. But it's not clear that # flipping all the MMU features to static_key_false won't introduce # other bugs. # # But for now just switch to early_mmu_has_feature() in set_kuap(), that # avoids all the problems with jump labels. It adds the overhead of a # global lookup and test, but that's probably trivial compared to the # writes to the AMR anyway. # # Fixes: 890274c2dc4c ("powerpc/64s: Implement KUAP for Radix MMU") # Signed-off-by: Michael Ellerman # < /opt/cross/kisskb/gcc-4.6.3-nolibc/m68k-linux/bin/m68k-linux-gcc --version # < /opt/cross/kisskb/gcc-4.6.3-nolibc/m68k-linux/bin/m68k-linux-ld --version # < git log --format=%s --max-count=1 a5a1fb260210893015872209514f73b55ab2138e # < make -s -j 120 ARCH=m68k O=/kisskb/build/powerpc-next_m68k-defconfig_m68k CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/m68k-linux/bin/m68k-linux- defconfig arch/m68k/configs/multi_defconfig:333:warning: symbol value 'm' invalid for NET_DEVLINK arch/m68k/configs/multi_defconfig:534:warning: symbol value 'm' invalid for FS_ENCRYPTION # make -s -j 120 ARCH=m68k O=/kisskb/build/powerpc-next_m68k-defconfig_m68k CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/m68k-linux/bin/m68k-linux- :1478:2: warning: #warning syscall pidfd_send_signal not implemented [-Wcpp] :1481:2: warning: #warning syscall io_uring_setup not implemented [-Wcpp] :1484:2: warning: #warning syscall io_uring_enter not implemented [-Wcpp] :1487:2: warning: #warning syscall io_uring_register not implemented [-Wcpp] /kisskb/src/arch/m68k/mvme147/config.c: In function 'mvme147_hwclk': /kisskb/src/arch/m68k/mvme147/config.c:150:2: warning: #warning check me! [-Wcpp] /kisskb/src/arch/m68k/mvme16x/config.c: In function 'mvme16x_hwclk': /kisskb/src/arch/m68k/mvme16x/config.c:397:2: warning: #warning check me! [-Wcpp] /kisskb/src/kernel/printk/printk.c: In function 'devkmsg_sysctl_set_loglvl': /kisskb/src/kernel/printk/printk.c:187:16: warning: 'old' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/ipc/shm.c: In function 'ksys_shmdt': /kisskb/src/ipc/shm.c:1712:59: warning: 'file' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/lib/mpi/mpicoder.c: In function 'mpi_read_raw_from_sgl': /kisskb/src/lib/mpi/mpicoder.c:336:12: warning: 'buff' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/net/core/gen_stats.c: In function '__gnet_stats_copy_basic': /kisskb/src/net/core/gen_stats.c:161:19: warning: 'seq' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/drivers/net/ethernet/8390/lib8390.c:201:12: warning: '__ei_open' defined but not used [-Wunused-function] /kisskb/src/drivers/net/ethernet/8390/lib8390.c:230:12: warning: '__ei_close' defined but not used [-Wunused-function] /kisskb/src/drivers/net/ethernet/8390/lib8390.c:254:13: warning: '__ei_tx_timeout' defined but not used [-Wunused-function] /kisskb/src/drivers/net/ethernet/8390/lib8390.c:300:20: warning: '__ei_start_xmit' defined but not used [-Wunused-function] /kisskb/src/drivers/net/ethernet/8390/lib8390.c:509:13: warning: '__ei_poll' defined but not used [-Wunused-function] /kisskb/src/drivers/net/ethernet/8390/lib8390.c:850:33: warning: '__ei_get_stats' defined but not used [-Wunused-function] /kisskb/src/drivers/net/ethernet/8390/lib8390.c:950:13: warning: '__ei_set_multicast_list' defined but not used [-Wunused-function] /kisskb/src/drivers/net/ethernet/8390/lib8390.c:988:27: warning: '____alloc_ei_netdev' defined but not used [-Wunused-function] /kisskb/src/fs/ocfs2/alloc.c: In function 'ocfs2_trim_mainbm': /kisskb/src/fs/ocfs2/alloc.c:7604:17: warning: 'first_bit' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/fs/proc/inode.c: In function 'proc_reg_open': /kisskb/src/include/linux/list.h:65:12: warning: 'pdeo' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/fs/proc/inode.c:337:21: note: 'pdeo' was declared here /kisskb/src/mm/mprotect.c: In function 'change_pte_range': /kisskb/src/mm/mprotect.c:42:20: warning: unused variable 'mm' [-Wunused-variable] /kisskb/src/net/core/dev.c: In function 'validate_xmit_skb_list': /kisskb/src/net/core/dev.c:3405:15: warning: 'tail' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/net/core/filter.c: In function 'bpf_clear_redirect_map': /kisskb/src/net/core/filter.c:3479:4: warning: value computed is not used [-Wunused-value] /kisskb/src/fs/ocfs2/file.c: In function 'ocfs2_file_write_iter': /kisskb/src/fs/ocfs2/file.c:2386:3: warning: value computed is not used [-Wunused-value] /kisskb/src/net/ipv4/ip_output.c: In function '__ip_append_data.isra.40': /kisskb/src/include/linux/skbuff.h:1397:6: warning: 'extra_uref' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/net/ipv4/ip_output.c:885:14: note: 'extra_uref' was declared here /kisskb/src/net/ipv6/ip6_output.c: In function '__ip6_append_data.isra.38': /kisskb/src/include/linux/skbuff.h:1397:6: warning: 'extra_uref' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/net/ipv6/ip6_output.c:1276:14: note: 'extra_uref' was declared here /kisskb/src/kernel/acct.c: In function 'acct_pin_kill': /kisskb/src/kernel/acct.c:177:2: warning: value computed is not used [-Wunused-value] /kisskb/src/lib/rhashtable.c: In function 'rht_deferred_worker': /kisskb/src/lib/rhashtable.c:264:2: warning: 'next' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/lib/rhashtable.c:229:28: note: 'next' was declared here /kisskb/src/fs/udf/unicode.c: In function 'udf_name_conv_char': /kisskb/src/fs/udf/unicode.c:132:8: warning: 'c' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/drivers/net/macsec.c: In function 'macsec_del_rxsa': /kisskb/src/drivers/net/macsec.c:1926:2: warning: 'assoc_num' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/drivers/net/macsec.c:1926:2: warning: 'rx_sc' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/drivers/net/macsec.c: In function 'macsec_del_txsa': /kisskb/src/drivers/net/macsec.c:2003:2: warning: 'assoc_num' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/drivers/net/macsec.c:2003:2: warning: 'tx_sc' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/drivers/net/macsec.c: In function 'macsec_upd_txsa': /kisskb/src/drivers/net/macsec.c:2068:5: warning: 'assoc_num' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/drivers/net/macsec.c:2068:24: warning: 'tx_sc' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/drivers/net/macsec.c:2069:21: warning: 'secy' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/drivers/net/tun.c: In function 'tun_get_user': /kisskb/src/drivers/net/tun.c:1842:30: warning: 'copylen' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/drivers/net/tun.c:1535:31: warning: 'linear' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/drivers/net/tun.c:1755:46: note: 'linear' was declared here /kisskb/src/net/sctp/output.c: In function 'sctp_packet_config': /kisskb/src/include/net/sock.h:1949:19: warning: 'sk' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/net/sctp/output.c:94:15: note: 'sk' was declared here /kisskb/src/fs/posix_acl.c: In function 'get_acl': /kisskb/src/fs/posix_acl.c:147:3: warning: value computed is not used [-Wunused-value] Completed OK # rm -rf /kisskb/build/powerpc-next_m68k-defconfig_m68k # Build took: 0:00:25.605173