Buildresult: linus/um-allmodconfig/um-x86_64 built on Jan 24 2019, 08:49

kisskb

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Status:	OK
Date/Time:	Jan 24 2019, 08:49
Duration:	0:04:53.529201
Builder:	ka2
Revision:	Revert "Change mincore() to count "mapped" pages rather than "cached" pages" (`30bac164aca750892b93eef350439a0562a68647)`
Target:	linus/um-allmodconfig/um-x86_64
Branch:	linus
Compiler:	um-x86_64 (x86_64-linux-gcc.br_real (Buildroot 2017.05) 5.4.0 / GNU ld (GNU Binutils) 2.27)
Config:	allmodconfig (download)
Log:	Download original Possible warnings (9) arch/um/kernel/skas/uaccess.c:62:10: warning: unused variable 'buf' [-Wunused-variable] arch/um/os-Linux/umid.c:138:2: warning: ISO C90 forbids variable length array 'file' [-Wvla] arch/um/os-Linux/umid.c:213:2: warning: ISO C90 forbids variable length array 'file' [-Wvla] arch/um/os-Linux/umid.c:388:2: warning: ISO C90 forbids variable length array 'dir' [-Wvla] kernel/cgroup/cgroup-v1.c:1263:3: warning: 'root' may be used uninitialized in this function [-Wmaybe-uninitialized] kernel/bpf/verifier.c:5065:4: warning: 'prev_offset' may be used uninitialized in this function [-Wmaybe-uninitialized] security/apparmor/policy_unpack.c:496:9: warning: 'pos' may be used uninitialized in this function [-Wmaybe-uninitialized] lib/lz4/lz4hc_compress.c:579:1: warning: the frame size of 2144 bytes is larger than 2048 bytes [-Wframe-larger-than=] drivers/i2c/i2c-core-base.c:235:5: warning: 'ret' may be used uninitialized in this function [-Wmaybe-uninitialized] Full Log # git rev-parse -q --verify 30bac164aca750892b93eef350439a0562a68647^{commit} 30bac164aca750892b93eef350439a0562a68647 already have revision, skipping fetch # git checkout -q -f -B kisskb 30bac164aca750892b93eef350439a0562a68647 # git clean -qxdf # < git log -1 # commit 30bac164aca750892b93eef350439a0562a68647 # Author: Linus Torvalds <torvalds@linux-foundation.org> # Date: Thu Jan 24 09:04:37 2019 +1300 # # Revert "Change mincore() to count "mapped" pages rather than "cached" pages" # # This reverts commit 574823bfab82d9d8fa47f422778043fbb4b4f50e. # # It turns out that my hope that we could just remove the code that # exposes the cache residency status from mincore() was too optimistic. # # There are various random users that want it, and one example would be # the Netflix database cluster maintenance. To quote Josh Snyder: # # "For Netflix, losing accurate information from the mincore syscall # would lengthen database cluster maintenance operations from days to # months. We rely on cross-process mincore to migrate the contents of a # page cache from machine to machine, and across reboots. # # To do this, I wrote and maintain happycache [1], a page cache # dumper/loader tool. It is quite similar in architecture to pgfincore, # except that it is agnostic to workload. The gist of happycache's # operation is "produce a dump of residence status for each page, do # some operation, then reload exactly the same pages which were present # before." happycache is entirely dependent on accurate reporting of the # in-core status of file-backed pages, as accessed by another process. # # We primarily use happycache with Cassandra, which (like Postgres + # pgfincore) relies heavily on OS page cache to reduce disk accesses. # Because our workloads never experience a cold page cache, we are able # to provision hardware for a peak utilization level that is far lower # than the hypothetical "every query is a cache miss" peak. # # A database warmed by happycache can be ready for service in seconds # (bounded only by the performance of the drives and the I/O subsystem), # with no period of in-service degradation. By contrast, putting a # database in service without a page cache entails a potentially # unbounded period of degradation (at Netflix, the time to populate a # single node's cache via natural cache misses varies by workload from # hours to weeks). If a single node upgrade were to take weeks, then # upgrading an entire cluster would take months. Since we want to apply # security upgrades (and other things) on a somewhat tighter schedule, # we would have to develop more complex solutions to provide the same # functionality already provided by mincore. # # At the bottom line, happycache is designed to benignly exploit the # same information leak documented in the paper [2]. I think it makes # perfect sense to remove cross-process mincore functionality from # unprivileged users, but not to remove it entirely" # # We do have an alternate approach that limits the cache residency # reporting only to processes that have write permissions to the file, so # we can fix the original information leak issue that way. It involves # _adding_ code rather than removing it, which is sad, but hey, at least # we haven't found any users that would find the restrictions # unacceptable. # # So revert the optimistic first approach to make room for that alternate # fix instead. # # Reported-by: Josh Snyder <joshs@netflix.com> # Cc: Jiri Kosina <jikos@kernel.org> # Cc: Dominique Martinet <asmadeus@codewreck.org> # Cc: Andy Lutomirski <luto@amacapital.net> # Cc: Dave Chinner <david@fromorbit.com> # Cc: Kevin Easton <kevin@guarana.org> # Cc: Matthew Wilcox <willy@infradead.org> # Cc: Cyril Hrubis <chrubis@suse.cz> # Cc: Vlastimil Babka <vbabka@suse.cz> # Cc: Tejun Heo <tj@kernel.org> # Cc: Kirill A. Shutemov <kirill@shutemov.name> # Cc: Daniel Gruss <daniel@gruss.cc> # Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> # < /opt/cross/kisskb/fe-x86-64-core-i7-2017.05/bin/x86_64-linux-gcc --version # < /opt/cross/kisskb/fe-x86-64-core-i7-2017.05/bin/x86_64-linux-ld --version # < git log --format=%s --max-count=1 30bac164aca750892b93eef350439a0562a68647 # < make -s -j 48 ARCH=um O=/kisskb/build/linus_um-allmodconfig_um-x86_64 CROSS_COMPILE=/opt/cross/kisskb/fe-x86-64-core-i7-2017.05/bin/x86_64-linux- SUBARCH=x86_64 allmodconfig # Added to kconfig CONFIG_STANDALONE=y # Added to kconfig CONFIG_KCOV=n # Added to kconfig CONFIG_GCC_PLUGINS=n # Added to kconfig CONFIG_GCC_PLUGIN_CYC_COMPLEXITY=n # Added to kconfig CONFIG_GCC_PLUGIN_SANCOV=n # Added to kconfig CONFIG_GCC_PLUGIN_LATENT_ENTROPY=n # Added to kconfig CONFIG_GCC_PLUGIN_STRUCTLEAK=n # Added to kconfig CONFIG_GCC_PLUGIN_RANDSTRUCT=n # Added to kconfig CONFIG_UML_NET=n # Added to kconfig CONFIG_UML_NET_ETHERTAP=n # Added to kconfig CONFIG_UML_NET_TUNTAP=n # Added to kconfig CONFIG_UML_NET_SLIP=n # Added to kconfig CONFIG_UML_NET_DAEMON=n # Added to kconfig CONFIG_UML_NET_VDE=n # Added to kconfig CONFIG_UML_NET_MCAST=n # Added to kconfig CONFIG_UML_NET_PCAP=n # Added to kconfig CONFIG_UML_NET_SLIRP=n # Added to kconfig CONFIG_GCOV_KERNEL=n # yes \n \| make -s -j 48 ARCH=um O=/kisskb/build/linus_um-allmodconfig_um-x86_64 CROSS_COMPILE=/opt/cross/kisskb/fe-x86-64-core-i7-2017.05/bin/x86_64-linux- SUBARCH=x86_64 oldconfig yes: standard output: Broken pipe # make -s -j 48 ARCH=um O=/kisskb/build/linus_um-allmodconfig_um-x86_64 CROSS_COMPILE=/opt/cross/kisskb/fe-x86-64-core-i7-2017.05/bin/x86_64-linux- SUBARCH=x86_64 /kisskb/src/arch/um/kernel/skas/uaccess.c: In function 'do_op_one_page': /kisskb/src/arch/um/kernel/skas/uaccess.c:62:10: warning: unused variable 'buf' [-Wunused-variable] jmp_buf buf; ^ /kisskb/src/arch/um/os-Linux/umid.c: In function 'is_umdir_used': /kisskb/src/arch/um/os-Linux/umid.c:138:2: warning: ISO C90 forbids variable length array 'file' [-Wvla] char file[strlen(uml_dir) + UMID_LEN + sizeof("/pid\0")]; ^ /kisskb/src/arch/um/os-Linux/umid.c: In function 'create_pid_file': /kisskb/src/arch/um/os-Linux/umid.c:213:2: warning: ISO C90 forbids variable length array 'file' [-Wvla] char file[strlen(uml_dir) + UMID_LEN + sizeof("/pid\0")]; ^ /kisskb/src/arch/um/os-Linux/umid.c: In function 'remove_umid_dir': /kisskb/src/arch/um/os-Linux/umid.c:388:2: warning: ISO C90 forbids variable length array 'dir' [-Wvla] char dir[strlen(uml_dir) + UMID_LEN + 1], err; ^ /kisskb/src/kernel/cgroup/cgroup-v1.c: In function 'cgroup1_mount': /kisskb/src/kernel/cgroup/cgroup-v1.c:1263:3: warning: 'root' may be used uninitialized in this function [-Wmaybe-uninitialized] percpu_ref_reinit(&root->cgrp.self.refcnt); ^ /kisskb/src/kernel/bpf/verifier.c: In function 'check_btf_info': /kisskb/src/kernel/bpf/verifier.c:5065:4: warning: 'prev_offset' may be used uninitialized in this function [-Wmaybe-uninitialized] verbose(env, ^ /kisskb/src/kernel/bpf/verifier.c:5000:38: note: 'prev_offset' was declared here u32 i, nfuncs, urec_size, min_size, prev_offset; ^ /kisskb/src/security/apparmor/policy_unpack.c: In function 'unpack_trans_table': /kisskb/src/security/apparmor/policy_unpack.c:496:9: warning: 'pos' may be used uninitialized in this function [-Wmaybe-uninitialized] str[pos] = ':'; ^ /kisskb/src/lib/lz4/lz4hc_compress.c: In function 'LZ4HC_compress_generic': /kisskb/src/lib/lz4/lz4hc_compress.c:579:1: warning: the frame size of 2144 bytes is larger than 2048 bytes [-Wframe-larger-than=] } ^ /kisskb/src/drivers/i2c/i2c-core-base.c: In function 'i2c_generic_scl_recovery': /kisskb/src/drivers/i2c/i2c-core-base.c:235:5: warning: 'ret' may be used uninitialized in this function [-Wmaybe-uninitialized] if (ret == -EOPNOTSUPP) ^ LINK linux Completed OK # rm -rf /kisskb/build/linus_um-allmodconfig_um-x86_64 # Build took: 0:04:53.529201

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