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03d2730b44
Robin Hack discovered Samba would enter an infinite loop processing
certain quota-related requests. We eventually tracked this down to a
glibc issue.
Running a (simplified) test case under strace shows that /etc/passwd
is continuously opened and closed:
…
open("/etc/passwd", O_RDONLY|O_CLOEXEC) = 3
lseek(3, 0, SEEK_CUR) = 0
read(3, "root❌0:0:root:/root:/bin/bash\n"..., 4096) = 2717
lseek(3, 2717, SEEK_SET) = 2717
close(3) = 0
open("/etc/passwd", O_RDONLY|O_CLOEXEC) = 3
lseek(3, 0, SEEK_CUR) = 0
lseek(3, 0, SEEK_SET) = 0
read(3, "root❌0:0:root:/root:/bin/bash\n"..., 4096) = 2717
lseek(3, 2717, SEEK_SET) = 2717
close(3) = 0
open("/etc/passwd", O_RDONLY|O_CLOEXEC) = 3
lseek(3, 0, SEEK_CUR) = 0
…
The lookup function implementation in
nss/nss_files/files-XXX.c:DB_LOOKUP has code to prevent that. It is
supposed skip closing the input file if it was already open.
/* Reset file pointer to beginning or open file. */ \
status = internal_setent (keep_stream); \
\
if (status == NSS_STATUS_SUCCESS) \
{ \
/* Tell getent function that we have repositioned the file pointer. */ \
last_use = getby; \
\
while ((status = internal_getent (result, buffer, buflen, errnop \
H_ERRNO_ARG EXTRA_ARGS_VALUE)) \
== NSS_STATUS_SUCCESS) \
{ break_if_match } \
\
if (! keep_stream) \
internal_endent (); \
} \
keep_stream is initialized from the stayopen flag in internal_setent.
internal_setent is called from the set*ent implementation as:
status = internal_setent (stayopen);
However, for non-host database, this flag is always 0, per the
STAYOPEN magic in nss/getXXent_r.c.
Thus, the fix is this:
- status = internal_setent (stayopen);
+ status = internal_setent (1);
This is not a behavioral change even for the hosts database (where the
application can specify the stayopen flag) because with a call to
sethostent(0), the file handle is still not closed in the
implementation of gethostent.
124 lines
3.9 KiB
Makefile
124 lines
3.9 KiB
Makefile
# Copyright (C) 1996-2015 Free Software Foundation, Inc.
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# This file is part of the GNU C Library.
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# The GNU C Library is free software; you can redistribute it and/or
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# modify it under the terms of the GNU Lesser General Public
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# License as published by the Free Software Foundation; either
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# version 2.1 of the License, or (at your option) any later version.
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# The GNU C Library is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# Lesser General Public License for more details.
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# You should have received a copy of the GNU Lesser General Public
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# License along with the GNU C Library; if not, see
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# <http://www.gnu.org/licenses/>.
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#
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# Makefile for name service switch.
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#
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subdir := nss
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include ../Makeconfig
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headers := nss.h
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# This is the trivial part which goes into libc itself.
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routines = nsswitch getnssent getnssent_r digits_dots \
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$(addsuffix -lookup,$(databases))
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# These are the databases that go through nss dispatch.
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# Caution: if you add a database here, you must add its real name
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# in databases.def, too.
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databases = proto service hosts network grp pwd ethers \
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spwd netgrp alias sgrp
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ifneq (,$(filter sunrpc,$(subdirs)))
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databases += key rpc
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have-sunrpc := 1
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else
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have-sunrpc := 0
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endif
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CPPFLAGS-getent.c = -DHAVE_SUNRPC=$(have-sunrpc)
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others := getent makedb
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install-bin := getent makedb
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makedb-modules = xmalloc hash-string
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extra-objs += $(makedb-modules:=.o)
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tests = test-netdb tst-nss-test1 test-digits-dots tst-nss-getpwent
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xtests = bug-erange
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# Specify rules for the nss_* modules. We have some services.
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services := files db
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extra-libs = $(services:%=libnss_%)
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# These libraries will be built in the `others' pass rather than
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# the `lib' pass, because they depend on libc.so being built already.
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extra-libs-others = $(extra-libs)
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# The sources are found in the appropriate subdir.
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subdir-dirs = $(services:%=nss_%)
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vpath %.c $(subdir-dirs) ../locale/programs ../intl
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libnss_files-routines := $(addprefix files-,$(databases)) \
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files-initgroups files-have_o_cloexec files-init
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libnss_db-dbs := $(addprefix db-,\
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$(filter-out hosts network key alias,\
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$(databases))) \
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db-initgroups
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libnss_db-routines := $(libnss_db-dbs) db-open db-init hash-string
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generated += $(filter-out db-alias.c db-netgrp.c, \
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$(addsuffix .c,$(libnss_db-dbs)))
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install-others += $(inst_vardbdir)/Makefile
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# Build static module into libc if requested
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libnss_files-inhibit-o = $(filter-out .os,$(object-suffixes))
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libnss_db-inhibit-o = $(filter-out .os,$(object-suffixes))
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ifeq ($(build-static-nss),yes)
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routines += $(libnss_files-routines)
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static-only-routines += $(libnss_files-routines)
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tests-static = tst-nss-static
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tests += $(tests-static)
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endif
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include ../Rules
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ifeq (yes,$(have-selinux))
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LDLIBS-makedb := -lselinux
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endif
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libnss-libc = $(common-objpfx)linkobj/libc.so
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# Target-specific variable setting to link objects using deprecated
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# RPC interfaces with the version of libc.so that makes them available
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# for new links:
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$(services:%=$(objpfx)libnss_%.so): libc-for-link = $(libnss-libc)
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$(objpfx)libnss_db.so: $(objpfx)libnss_files.so
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$(libnss_db-dbs:%=$(objpfx)%.c): $(objpfx)db-%.c: nss_files/files-%.c
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@rm -f $@.new
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(echo '#define EXTERN_PARSER';\
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echo '#define GENERIC "../nss_db/db-XXX.c"';\
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echo '#include "$<"') > $@.new
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mv -f $@.new $@
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$(objpfx)makedb: $(makedb-modules:%=$(objpfx)%.o)
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$(inst_vardbdir)/Makefile: db-Makefile $(+force)
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$(do-install)
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libof-nss_test1 = extramodules
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$(objpfx)/libnss_test1.so: $(objpfx)nss_test1.os $(link-libc-deps)
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$(build-module)
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ifdef libnss_test1.so-version
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$(objpfx)/libnss_test1.so$(libnss_test1.so-version): $(objpfx)/libnss_test1.so
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$(make-link)
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endif
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$(objpfx)tst-nss-test1.out: $(objpfx)/libnss_test1.so$(libnss_test1.so-version)
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