Message-ID: <fa3bd4b1-362a-5262-415e-fef9999e25f3@csgroup.eu>
Date:   Wed, 31 Aug 2022 17:16:24 +0000
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Song Liu <song@...nel.org>
CC:     "live-patching@...r.kernel.org" <live-patching@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "pmladek@...e.com" <pmladek@...e.com>,
        "jikos@...nel.org" <jikos@...nel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "joe.lawrence@...hat.com" <joe.lawrence@...hat.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        "mbenes@...e.cz" <mbenes@...e.cz>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "jpoimboe@...nel.org" <jpoimboe@...nel.org>
Subject: Re: [PATCH v5] livepatch: Clear relocation targets on a module
 removal



Le 31/08/2022 à 19:05, Song Liu a écrit :
> On Wed, Aug 31, 2022 at 1:01 AM Christophe Leroy
> <christophe.leroy@...roup.eu> wrote:
>>
>>
>>
>> Le 30/08/2022 à 20:53, Song Liu a écrit :
>>> From: Miroslav Benes <mbenes@...e.cz>
>>>
>>> Josh reported a bug:
>>>
>>>     When the object to be patched is a module, and that module is
>>>     rmmod'ed and reloaded, it fails to load with:
>>>
>>>     module: x86/modules: Skipping invalid relocation target, existing value is nonzero for type 2, loc 00000000ba0302e9, val ffffffffa03e293c
>>>     livepatch: failed to initialize patch 'livepatch_nfsd' for module 'nfsd' (-8)
>>>     livepatch: patch 'livepatch_nfsd' failed for module 'nfsd', refusing to load module 'nfsd'
>>>
>>>     The livepatch module has a relocation which references a symbol
>>>     in the _previous_ loading of nfsd. When apply_relocate_add()
>>>     tries to replace the old relocation with a new one, it sees that
>>>     the previous one is nonzero and it errors out.
>>>
>>>     On ppc64le, we have a similar issue:
>>>
>>>     module_64: livepatch_nfsd: Expected nop after call, got e8410018 at e_show+0x60/0x548 [livepatch_nfsd]
>>>     livepatch: failed to initialize patch 'livepatch_nfsd' for module 'nfsd' (-8)
>>>     livepatch: patch 'livepatch_nfsd' failed for module 'nfsd', refusing to load module 'nfsd'
>>>
>>> He also proposed three different solutions. We could remove the error
>>> check in apply_relocate_add() introduced by commit eda9cec4c9a1
>>> ("x86/module: Detect and skip invalid relocations"). However the check
>>> is useful for detecting corrupted modules.
>>>
>>> We could also deny the patched modules to be removed. If it proved to be
>>> a major drawback for users, we could still implement a different
>>> approach. The solution would also complicate the existing code a lot.
>>>
>>> We thus decided to reverse the relocation patching (clear all relocation
>>> targets on x86_64). The solution is not
>>> universal and is too much arch-specific, but it may prove to be simpler
>>> in the end.
>>>
>>> Reported-by: Josh Poimboeuf <jpoimboe@...hat.com>
>>> Signed-off-by: Miroslav Benes <mbenes@...e.cz>
>>> Signed-off-by: Song Liu <song@...nel.org>
>>>
>>> ---
>>>
>>> NOTE: powerpc code has not be tested.
>>>
>>> Changes v4 = v5:
>>> 1. Fix compile with powerpc.
>>
>> Not completely it seems.
>>
>>     CC      kernel/livepatch/core.o
>> kernel/livepatch/core.c: In function 'klp_clear_object_relocations':
>> kernel/livepatch/core.c:352:50: error: passing argument 1 of
>> 'clear_relocate_add' from incompatible pointer type
>> [-Werror=incompatible-pointer-types]
>>     352 |                 clear_relocate_add(pmod->klp_info->sechdrs,
>>         |                                    ~~~~~~~~~~~~~~^~~~~~~~~
>>         |                                                  |
>>         |                                                  Elf32_Shdr *
>> {aka struct elf32_shdr *}
>> In file included from kernel/livepatch/core.c:19:
>> ./include/linux/moduleloader.h:76:37: note: expected 'Elf64_Shdr *' {aka
>> 'struct elf64_shdr *'} but argument is of type 'Elf32_Shdr *' {aka
>> 'struct elf32_shdr *'}
>>      76 | void clear_relocate_add(Elf64_Shdr *sechdrs,
>>         |                         ~~~~~~~~~~~~^~~~~~~
>> cc1: some warnings being treated as errors
>>
>>
>> Fixup:
>>
>> diff --git a/include/linux/moduleloader.h b/include/linux/moduleloader.h
>> index d22b36b84b4b..958e6da7f475 100644
>> --- a/include/linux/moduleloader.h
>> +++ b/include/linux/moduleloader.h
>> @@ -73,7 +73,7 @@ int apply_relocate_add(Elf_Shdr *sechdrs,
>>                         unsigned int relsec,
>>                         struct module *mod);
>>    #ifdef CONFIG_LIVEPATCH
>> -void clear_relocate_add(Elf64_Shdr *sechdrs,
>> +void clear_relocate_add(Elf_Shdr *sechdrs,
>>                     const char *strtab,
>>                     unsigned int symindex,
>>                     unsigned int relsec,
>>
>>
>> But then the link fails.
>>
>>     LD      .tmp_vmlinux.kallsyms1
>> powerpc64-linux-ld: kernel/livepatch/core.o: in function
>> `klp_cleanup_module_patches_limited':
>> core.c:(.text+0xdb4): undefined reference to `clear_relocate_add'
> 
> Hmm.. I am not seeing either error. Could you please share your .config file?
> 

defconfig follows:

# CONFIG_LOCALVERSION_AUTO is not set
CONFIG_SYSVIPC=y
CONFIG_POSIX_MQUEUE=y
CONFIG_NO_HZ=y
CONFIG_HIGH_RES_TIMERS=y
CONFIG_IKCONFIG=y
CONFIG_IKCONFIG_PROC=y
CONFIG_LOG_BUF_SHIFT=14
CONFIG_BLK_DEV_INITRD=y
CONFIG_KALLSYMS_ALL=y
CONFIG_PROFILING=y
CONFIG_ALTIVEC=y
# CONFIG_PPC_CHRP is not set
CONFIG_CPU_FREQ=y
CONFIG_CPU_FREQ_GOV_POWERSAVE=y
CONFIG_CPU_FREQ_GOV_USERSPACE=y
CONFIG_CPU_FREQ_PMAC=y
CONFIG_GEN_RTC=y
CONFIG_HIGHMEM=y
CONFIG_HIBERNATION=y
CONFIG_PM_DEBUG=y
CONFIG_APM_EMULATION=y
CONFIG_LIVEPATCH=y
CONFIG_MODULES=y
CONFIG_MODULE_UNLOAD=y
CONFIG_MODULE_FORCE_UNLOAD=y
CONFIG_PARTITION_ADVANCED=y
CONFIG_BINFMT_MISC=m
# CONFIG_COMPAT_BRK is not set
CONFIG_NET=y
CONFIG_PACKET=y
CONFIG_UNIX=y
CONFIG_XFRM_USER=y
CONFIG_NET_KEY=y
CONFIG_INET=y
CONFIG_IP_MULTICAST=y
CONFIG_SYN_COOKIES=y
CONFIG_INET_AH=y
CONFIG_INET_ESP=y
# CONFIG_IPV6 is not set
CONFIG_NETFILTER=y
CONFIG_NF_CONNTRACK=m
CONFIG_NF_CONNTRACK_FTP=m
CONFIG_NF_CONNTRACK_IRC=m
CONFIG_NF_CONNTRACK_TFTP=m
CONFIG_NF_CT_NETLINK=m
CONFIG_NETFILTER_XT_TARGET_CLASSIFY=m
CONFIG_NETFILTER_XT_TARGET_MARK=m
CONFIG_NETFILTER_XT_TARGET_NFLOG=m
CONFIG_NETFILTER_XT_TARGET_NFQUEUE=m
CONFIG_NETFILTER_XT_TARGET_TRACE=m
CONFIG_NETFILTER_XT_TARGET_TCPMSS=m
CONFIG_NETFILTER_XT_TARGET_TCPOPTSTRIP=m
CONFIG_NETFILTER_XT_MATCH_COMMENT=m
CONFIG_NETFILTER_XT_MATCH_CONNLIMIT=m
CONFIG_NETFILTER_XT_MATCH_CONNTRACK=m
CONFIG_NETFILTER_XT_MATCH_DSCP=m
CONFIG_NETFILTER_XT_MATCH_ESP=m
CONFIG_NETFILTER_XT_MATCH_HELPER=m
CONFIG_NETFILTER_XT_MATCH_IPRANGE=m
CONFIG_NETFILTER_XT_MATCH_LENGTH=m
CONFIG_NETFILTER_XT_MATCH_LIMIT=m
CONFIG_NETFILTER_XT_MATCH_MAC=m
CONFIG_NETFILTER_XT_MATCH_MARK=m
CONFIG_NETFILTER_XT_MATCH_MULTIPORT=m
CONFIG_NETFILTER_XT_MATCH_OWNER=m
CONFIG_NETFILTER_XT_MATCH_POLICY=m
CONFIG_NETFILTER_XT_MATCH_PKTTYPE=m
CONFIG_NETFILTER_XT_MATCH_RATEEST=m
CONFIG_NETFILTER_XT_MATCH_REALM=m
CONFIG_NETFILTER_XT_MATCH_RECENT=m
CONFIG_NETFILTER_XT_MATCH_SCTP=m
CONFIG_NETFILTER_XT_MATCH_STRING=m
CONFIG_NETFILTER_XT_MATCH_TCPMSS=m
CONFIG_NETFILTER_XT_MATCH_TIME=m
CONFIG_NETFILTER_XT_MATCH_U32=m
CONFIG_IP_NF_IPTABLES=m
CONFIG_IP_NF_MATCH_AH=m
CONFIG_IP_NF_MATCH_ECN=m
CONFIG_IP_NF_MATCH_TTL=m
CONFIG_IP_NF_FILTER=m
CONFIG_IP_NF_TARGET_REJECT=m
CONFIG_IP_NF_MANGLE=m
CONFIG_IP_NF_TARGET_ECN=m
CONFIG_IP_NF_TARGET_TTL=m
CONFIG_IP_NF_RAW=m
CONFIG_IP_NF_ARPTABLES=m
CONFIG_IP_NF_ARPFILTER=m
CONFIG_IP_NF_ARP_MANGLE=m
CONFIG_IP_DCCP=m
CONFIG_BT=m
CONFIG_BT_RFCOMM=m
CONFIG_BT_RFCOMM_TTY=y
CONFIG_BT_BNEP=m
CONFIG_BT_BNEP_MC_FILTER=y
CONFIG_BT_BNEP_PROTO_FILTER=y
CONFIG_BT_HIDP=m
CONFIG_BT_HCIBCM203X=m
CONFIG_BT_HCIBFUSB=m
CONFIG_CFG80211=m
CONFIG_MAC80211=m
CONFIG_MAC80211_LEDS=y
CONFIG_PCCARD=m
CONFIG_YENTA=m
# CONFIG_STANDALONE is not set
CONFIG_CONNECTOR=y
CONFIG_MAC_FLOPPY=m
CONFIG_BLK_DEV_LOOP=y
CONFIG_BLK_DEV_RAM=y
CONFIG_BLK_DEV_SD=y
CONFIG_CHR_DEV_ST=y
CONFIG_BLK_DEV_SR=y
CONFIG_CHR_DEV_SG=y
CONFIG_SCSI_CONSTANTS=y
CONFIG_SCSI_FC_ATTRS=y
CONFIG_SCSI_AIC7XXX=m
CONFIG_AIC7XXX_CMDS_PER_DEVICE=253
CONFIG_AIC7XXX_RESET_DELAY_MS=15000
CONFIG_SCSI_SYM53C8XX_2=y
CONFIG_SCSI_SYM53C8XX_DMA_ADDRESSING_MODE=0
CONFIG_SCSI_MESH=y
CONFIG_SCSI_MAC53C94=y
CONFIG_ATA=y
CONFIG_PATA_MACIO=y
CONFIG_PATA_PDC2027X=y
CONFIG_PATA_WINBOND=y
CONFIG_PATA_PCMCIA=m
CONFIG_ATA_GENERIC=y
CONFIG_MD=y
CONFIG_BLK_DEV_MD=m
CONFIG_MD_LINEAR=m
CONFIG_MD_RAID0=m
CONFIG_MD_RAID1=m
CONFIG_MD_RAID10=m
CONFIG_MD_MULTIPATH=m
CONFIG_MD_FAULTY=m
CONFIG_BLK_DEV_DM=m
CONFIG_DM_CRYPT=m
CONFIG_DM_SNAPSHOT=m
CONFIG_DM_MIRROR=m
CONFIG_DM_ZERO=m
CONFIG_ADB=y
CONFIG_ADB_CUDA=y
CONFIG_ADB_PMU=y
CONFIG_ADB_PMU_LED=y
CONFIG_ADB_PMU_LED_DISK=y
CONFIG_PMAC_APM_EMU=m
CONFIG_PMAC_MEDIABAY=y
CONFIG_PMAC_BACKLIGHT=y
CONFIG_PMAC_BACKLIGHT_LEGACY=y
CONFIG_INPUT_ADBHID=y
CONFIG_MAC_EMUMOUSEBTN=y
CONFIG_THERM_WINDTUNNEL=m
CONFIG_THERM_ADT746X=m
CONFIG_PMAC_RACKMETER=m
CONFIG_NETDEVICES=y
CONFIG_DUMMY=m
CONFIG_TUN=m
CONFIG_PCNET32=y
CONFIG_MACE=y
CONFIG_BMAC=y
CONFIG_SUNGEM=y
CONFIG_PPP=y
CONFIG_PPP_BSDCOMP=m
CONFIG_PPP_DEFLATE=y
CONFIG_PPP_MULTILINK=y
CONFIG_PPP_ASYNC=y
CONFIG_PPP_SYNC_TTY=m
CONFIG_USB_USBNET=m
# CONFIG_USB_NET_CDC_SUBSET is not set
CONFIG_B43=m
CONFIG_B43LEGACY=m
CONFIG_P54_COMMON=m
CONFIG_INPUT_EVDEV=y
# CONFIG_KEYBOARD_ATKBD is not set
# CONFIG_MOUSE_PS2 is not set
CONFIG_MOUSE_APPLETOUCH=y
# CONFIG_SERIO_I8042 is not set
# CONFIG_SERIO_SERPORT is not set
CONFIG_SERIAL_8250=m
CONFIG_SERIAL_PMACZILOG=m
CONFIG_SERIAL_PMACZILOG_TTYS=y
CONFIG_I2C_CHARDEV=m
CONFIG_APM_POWER=y
CONFIG_BATTERY_PMU=y
CONFIG_HWMON=m
CONFIG_AGP=m
CONFIG_AGP_UNINORTH=m
CONFIG_DRM=m
CONFIG_DRM_RADEON=m
CONFIG_DRM_LEGACY=y
CONFIG_DRM_R128=m
CONFIG_FB=y
CONFIG_FB_OF=y
CONFIG_FB_CONTROL=y
CONFIG_FB_PLATINUM=y
CONFIG_FB_VALKYRIE=y
CONFIG_FB_CT65550=y
CONFIG_FB_IMSTT=y
CONFIG_FB_NVIDIA=y
CONFIG_FB_NVIDIA_I2C=y
CONFIG_FB_MATROX=y
CONFIG_FB_MATROX_MILLENIUM=y
CONFIG_FB_MATROX_MYSTIQUE=y
CONFIG_FB_RADEON=y
CONFIG_FB_ATY128=y
CONFIG_FB_ATY=y
CONFIG_FB_ATY_CT=y
CONFIG_FB_ATY_GX=y
CONFIG_FB_3DFX=y
# CONFIG_VGA_CONSOLE is not set
CONFIG_LOGO=y
CONFIG_SOUND=m
CONFIG_SND=m
CONFIG_SND_OSSEMUL=y
CONFIG_SND_MIXER_OSS=m
CONFIG_SND_PCM_OSS=m
CONFIG_SND_SEQUENCER=m
CONFIG_SND_SEQ_DUMMY=m
CONFIG_SND_SEQUENCER_OSS=m
CONFIG_SND_DUMMY=m
CONFIG_SND_POWERMAC=m
CONFIG_SND_AOA=m
CONFIG_SND_AOA_FABRIC_LAYOUT=m
CONFIG_SND_AOA_ONYX=m
CONFIG_SND_AOA_TAS=m
CONFIG_SND_AOA_TOONIE=m
CONFIG_SND_USB_AUDIO=m
CONFIG_HID_GYRATION=y
CONFIG_HID_NTRIG=y
CONFIG_HID_PANTHERLORD=y
CONFIG_HID_PETALYNX=y
CONFIG_HID_SAMSUNG=y
CONFIG_HID_SONY=y
CONFIG_HID_SUNPLUS=y
CONFIG_HID_TOPSEED=y
CONFIG_USB_DYNAMIC_MINORS=y
CONFIG_USB_MON=y
CONFIG_USB_EHCI_HCD=m
CONFIG_USB_EHCI_ROOT_HUB_TT=y
# CONFIG_USB_EHCI_HCD_PPC_OF is not set
CONFIG_USB_OHCI_HCD=y
CONFIG_USB_ACM=m
CONFIG_USB_PRINTER=m
CONFIG_USB_STORAGE=m
CONFIG_USB_STORAGE_ONETOUCH=m
CONFIG_USB_SERIAL=m
CONFIG_USB_SERIAL_VISOR=m
CONFIG_USB_SERIAL_IPAQ=m
CONFIG_USB_SERIAL_KEYSPAN_PDA=m
CONFIG_USB_SERIAL_KEYSPAN=m
CONFIG_USB_APPLEDISPLAY=m
CONFIG_LEDS_TRIGGER_DEFAULT_ON=y
CONFIG_EXT2_FS=y
CONFIG_EXT4_FS=y
CONFIG_EXT4_FS_POSIX_ACL=y
CONFIG_AUTOFS4_FS=m
CONFIG_FUSE_FS=m
CONFIG_ISO9660_FS=y
CONFIG_JOLIET=y
CONFIG_ZISOFS=y
CONFIG_UDF_FS=m
CONFIG_MSDOS_FS=m
CONFIG_VFAT_FS=m
CONFIG_PROC_KCORE=y
CONFIG_TMPFS=y
CONFIG_HFS_FS=m
CONFIG_HFSPLUS_FS=m
CONFIG_NFS_FS=y
CONFIG_NFS_V3_ACL=y
CONFIG_NFS_V4=y
CONFIG_NFSD=m
CONFIG_NFSD_V3_ACL=y
CONFIG_NFSD_V4=y
CONFIG_NLS_CODEPAGE_437=m
CONFIG_NLS_ISO8859_1=m
CONFIG_CRYPTO_PCBC=m
CONFIG_CRYPTO_MD4=m
CONFIG_CRYPTO_WP512=m
CONFIG_CRYPTO_BLOWFISH=m
CONFIG_CRYPTO_CAST5=m
CONFIG_CRYPTO_CAST6=m
CONFIG_CRYPTO_SERPENT=m
CONFIG_CRYPTO_TWOFISH=m
CONFIG_CRYPTO_DEFLATE=m
CONFIG_CRC_T10DIF=y
CONFIG_DEBUG_KERNEL=y
CONFIG_MAGIC_SYSRQ=y
CONFIG_DETECT_HUNG_TASK=y
CONFIG_FUNCTION_TRACER=y
CONFIG_XMON=y
CONFIG_XMON_DEFAULT=y
CONFIG_BOOTX_TEXT=y

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