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libc: Add O_PATH support for fgetxattr / fsetxattr

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Support O_PATH file descriptors when handling fgetxattr and fsetxattr.
This avoids requiring file read access to pull extended attributes.

This is needed to support O_PATH file descriptors when calling
SELinux's fgetfilecon() call. In particular, this allows the querying
and setting of SELinux file context by using something like the following
code:

  int dirfd = open("/path/to/dir", O_DIRECTORY);
  int fd = openat(dirfd, "file", O_PATH | O_NOFOLLOW);
  char *context;
  fgetfilecon(fd, &context);

This change was motivated by a comment in
https://android-review.googlesource.com/#/c/152680/1/toys/posix/ls.c

Change-Id: Ic0cdf9f9dd0e35a63b44a4c4a08400020041eddf
This commit is contained in:
Nick Kralevich 2015-05-31 13:43:13 -07:00
parent ef607cdae2
commit 2825f10b7f
18 changed files with 259 additions and 26 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
libc/Android.mk
View file

@ -129,8 +129,10 @@ libc_bionic_ndk_src_files := \
bionic/fchmod.cpp \
bionic/fchmodat.cpp \
bionic/ffs.cpp \
bionic/fgetxattr.cpp \
bionic/flockfile.cpp \
bionic/fpclassify.cpp \
bionic/fsetxattr.cpp \
bionic/ftruncate.cpp \
bionic/futimens.cpp \
bionic/getcwd.cpp \

4
libc/SYSCALLS.TXT
View file

@ -122,8 +122,8 @@ int fdatasync(int) all
int fchown:fchown32(int, uid_t, gid_t) arm,x86
int fchown:fchown(int, uid_t, gid_t) arm64,mips,mips64,x86_64
void sync(void) all
int fsetxattr(int, const char*, const void*, size_t, int) all
ssize_t fgetxattr(int, const char*, void*, size_t) all
int ___fsetxattr:fsetxattr(int, const char*, const void*, size_t, int) all
ssize_t ___fgetxattr:fgetxattr(int, const char*, void*, size_t) all
ssize_t flistxattr(int, char*, size_t) all
int fremovexattr(int, const char*) all

5
libc/arch-arm/syscalls/fgetxattr.S → libc/arch-arm/syscalls/___fgetxattr.S
View file

@ -2,7 +2,7 @@
#include <private/bionic_asm.h>
ENTRY(fgetxattr)
ENTRY(___fgetxattr)
mov ip, r7
ldr r7, =__NR_fgetxattr
swi #0
@ -11,4 +11,5 @@ ENTRY(fgetxattr)
bxls lr
neg r0, r0
b __set_errno_internal
END(fgetxattr)
END(___fgetxattr)
.hidden ___fgetxattr

5
libc/arch-arm/syscalls/fsetxattr.S → libc/arch-arm/syscalls/___fsetxattr.S
View file

@ -2,7 +2,7 @@
#include <private/bionic_asm.h>
ENTRY(fsetxattr)
ENTRY(___fsetxattr)
mov ip, sp
stmfd sp!, {r4, r5, r6, r7}
.cfi_def_cfa_offset 16
@ -19,4 +19,5 @@ ENTRY(fsetxattr)
bxls lr
neg r0, r0
b __set_errno_internal
END(fsetxattr)
END(___fsetxattr)
.hidden ___fsetxattr

5
libc/arch-arm64/syscalls/fgetxattr.S → libc/arch-arm64/syscalls/___fgetxattr.S
View file

@ -2,7 +2,7 @@
#include <private/bionic_asm.h>
ENTRY(fgetxattr)
ENTRY(___fgetxattr)
mov x8, __NR_fgetxattr
svc #0
@ -11,4 +11,5 @@ ENTRY(fgetxattr)
b.hi __set_errno_internal
ret
END(fgetxattr)
END(___fgetxattr)
.hidden ___fgetxattr

5
libc/arch-arm64/syscalls/fsetxattr.S → libc/arch-arm64/syscalls/___fsetxattr.S
View file

@ -2,7 +2,7 @@
#include <private/bionic_asm.h>
ENTRY(fsetxattr)
ENTRY(___fsetxattr)
mov x8, __NR_fsetxattr
svc #0
@ -11,4 +11,5 @@ ENTRY(fsetxattr)
b.hi __set_errno_internal
ret
END(fsetxattr)
END(___fsetxattr)
.hidden ___fsetxattr

5
libc/arch-mips/syscalls/fgetxattr.S → libc/arch-mips/syscalls/___fgetxattr.S
View file

@ -2,7 +2,7 @@
#include <private/bionic_asm.h>
ENTRY(fgetxattr)
ENTRY(___fgetxattr)
.set noreorder
.cpload t9
li v0, __NR_fgetxattr
@ -16,4 +16,5 @@ ENTRY(fgetxattr)
j t9
nop
.set reorder
END(fgetxattr)
END(___fgetxattr)
.hidden ___fgetxattr

5
libc/arch-mips/syscalls/fsetxattr.S → libc/arch-mips/syscalls/___fsetxattr.S
View file

@ -2,7 +2,7 @@
#include <private/bionic_asm.h>
ENTRY(fsetxattr)
ENTRY(___fsetxattr)
.set noreorder
.cpload t9
li v0, __NR_fsetxattr
@ -16,4 +16,5 @@ ENTRY(fsetxattr)
j t9
nop
.set reorder
END(fsetxattr)
END(___fsetxattr)
.hidden ___fsetxattr

5
libc/arch-mips64/syscalls/fgetxattr.S → libc/arch-mips64/syscalls/___fgetxattr.S
View file

@ -2,7 +2,7 @@
#include <private/bionic_asm.h>
ENTRY(fgetxattr)
ENTRY(___fgetxattr)
.set push
.set noreorder
li v0, __NR_fgetxattr
@ -22,4 +22,5 @@ ENTRY(fgetxattr)
j t9
move ra, t0
.set pop
END(fgetxattr)
END(___fgetxattr)
.hidden ___fgetxattr

5
libc/arch-mips64/syscalls/fsetxattr.S → libc/arch-mips64/syscalls/___fsetxattr.S
View file

@ -2,7 +2,7 @@
#include <private/bionic_asm.h>
ENTRY(fsetxattr)
ENTRY(___fsetxattr)
.set push
.set noreorder
li v0, __NR_fsetxattr
@ -22,4 +22,5 @@ ENTRY(fsetxattr)
j t9
move ra, t0
.set pop
END(fsetxattr)
END(___fsetxattr)
.hidden ___fsetxattr

5
libc/arch-x86/syscalls/fgetxattr.S → libc/arch-x86/syscalls/___fgetxattr.S
View file

@ -2,7 +2,7 @@
#include <private/bionic_asm.h>
ENTRY(fgetxattr)
ENTRY(___fgetxattr)
pushl %ebx
.cfi_def_cfa_offset 8
.cfi_rel_offset ebx, 0
@ -33,4 +33,5 @@ ENTRY(fgetxattr)
popl %ecx
popl %ebx
ret
END(fgetxattr)
END(___fgetxattr)
.hidden ___fgetxattr

5
libc/arch-x86/syscalls/fsetxattr.S → libc/arch-x86/syscalls/___fsetxattr.S
View file

@ -2,7 +2,7 @@
#include <private/bionic_asm.h>
ENTRY(fsetxattr)
ENTRY(___fsetxattr)
pushl %ebx
.cfi_def_cfa_offset 8
.cfi_rel_offset ebx, 0
@ -38,4 +38,5 @@ ENTRY(fsetxattr)
popl %ecx
popl %ebx
ret
END(fsetxattr)
END(___fsetxattr)
.hidden ___fsetxattr

5
libc/arch-x86_64/syscalls/fgetxattr.S → libc/arch-x86_64/syscalls/___fgetxattr.S
View file

@ -2,7 +2,7 @@
#include <private/bionic_asm.h>
ENTRY(fgetxattr)
ENTRY(___fgetxattr)
movq %rcx, %r10
movl $__NR_fgetxattr, %eax
syscall
@ -13,4 +13,5 @@ ENTRY(fgetxattr)
call __set_errno_internal
1:
ret
END(fgetxattr)
END(___fgetxattr)
.hidden ___fgetxattr

5
libc/arch-x86_64/syscalls/fsetxattr.S → libc/arch-x86_64/syscalls/___fsetxattr.S
View file

@ -2,7 +2,7 @@
#include <private/bionic_asm.h>
ENTRY(fsetxattr)
ENTRY(___fsetxattr)
movq %rcx, %r10
movl $__NR_fsetxattr, %eax
syscall
@ -13,4 +13,5 @@ ENTRY(fsetxattr)
call __set_errno_internal
1:
ret
END(fsetxattr)
END(___fsetxattr)
.hidden ___fsetxattr

59
libc/bionic/fgetxattr.cpp Normal file
View file

@ -0,0 +1,59 @@
/*
* Copyright (C) 2015 The Android Open Source Project
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/xattr.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
extern "C" ssize_t ___fgetxattr(int, const char*, void*, size_t);
ssize_t fgetxattr(int fd, const char *name, void *value, size_t size) {
int saved_errno = errno;
ssize_t result = ___fgetxattr(fd, name, value, size);
if ((result != -1) || (errno != EBADF)) {
return result;
}
// fd could be an O_PATH file descriptor, and the kernel
// may not directly support fgetxattr() on such a file descriptor.
// Use /proc/self/fd instead to emulate this support.
int fd_flag = fcntl(fd, F_GETFL);
if ((fd_flag == -1) || ((fd_flag & O_PATH) == 0)) {
errno = EBADF;
return -1;
}
char buf[40];
snprintf(buf, sizeof(buf), "/proc/self/fd/%d", fd);
errno = saved_errno;
return getxattr(buf, name, value, size);
}

59
libc/bionic/fsetxattr.cpp Normal file
View file

@ -0,0 +1,59 @@
/*
* Copyright (C) 2015 The Android Open Source Project
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/xattr.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
extern "C" int ___fsetxattr(int, const char*, const void*, size_t, int);
int fsetxattr(int fd, const char* name, const void* value, size_t size, int flags) {
int saved_errno = errno;
int result = ___fsetxattr(fd, name, value, size, flags);
if ((result == 0) || (errno != EBADF)) {
return result;
}
// fd could be an O_PATH file descriptor, and the kernel
// may not directly support fsetxattr() on such a file descriptor.
// Use /proc/self/fd instead to emulate this support.
int fd_flag = fcntl(fd, F_GETFL);
if ((fd_flag == -1) || ((fd_flag & O_PATH) == 0)) {
errno = EBADF;
return -1;
}
char buf[40];
snprintf(buf, sizeof(buf), "/proc/self/fd/%d", fd);
errno = saved_errno;
return setxattr(buf, name, value, size, flags);
}

1
tests/Android.mk
View file

@ -107,6 +107,7 @@ libBionicStandardTests_src_files := \
sys_time_test.cpp \
sys_types_test.cpp \
sys_vfs_test.cpp \
sys_xattr_test.cpp \
system_properties_test.cpp \
time_test.cpp \
uchar_test.cpp \

100
tests/sys_xattr_test.cpp Normal file
View file

@ -0,0 +1,100 @@
/*
* Copyright (C) 2015 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <gtest/gtest.h>
#include <sys/types.h>
#include <sys/xattr.h>
#include "TemporaryFile.h"
TEST(sys_xattr, setxattr) {
TemporaryFile tf;
char buf[10];
ASSERT_EQ(0, setxattr(tf.filename, "user.foo", "bar", 4, 0));
ASSERT_EQ(4, getxattr(tf.filename, "user.foo", buf, sizeof(buf)));
ASSERT_STREQ("bar", buf);
buf[0] = '\0';
ASSERT_EQ(4, lgetxattr(tf.filename, "user.foo", buf, sizeof(buf)));
ASSERT_STREQ("bar", buf);
}
TEST(sys_xattr, fsetxattr) {
TemporaryFile tf;
char buf[10];
ASSERT_EQ(0, fsetxattr(tf.fd, "user.foo", "bar", 4, 0));
ASSERT_EQ(4, fgetxattr(tf.fd, "user.foo", buf, sizeof(buf)));
ASSERT_STREQ("bar", buf);
}
TEST(sys_xattr, fsetxattr_zerobuf) {
TemporaryFile tf;
char buf[10];
ASSERT_EQ(0, fsetxattr(tf.fd, "user.foo", "", 0, 0));
ASSERT_EQ(0, fgetxattr(tf.fd, "user.foo", buf, sizeof(buf)));
}
TEST(sys_xattr, fsetxattr_toosmallbuf) {
TemporaryFile tf;
char buf[10];
ASSERT_EQ(0, fsetxattr(tf.fd, "user.foo", "01234567890123456789", 21, 0));
ASSERT_EQ(-1, fgetxattr(tf.fd, "user.foo", buf, sizeof(buf)));
ASSERT_EQ(ERANGE, errno);
}
TEST(sys_xattr, fsetxattr_invalidfd) {
char buf[10];
errno = 0;
ASSERT_EQ(-1, fsetxattr(65535, "user.foo", "0123", 5, 0));
ASSERT_EQ(EBADF, errno);
errno = 0;
ASSERT_EQ(-1, fgetxattr(65535, "user.foo", buf, sizeof(buf)));
ASSERT_EQ(EBADF, errno);
}
TEST(sys_xattr, fsetxattr_with_opath) {
TemporaryFile tf;
int fd = open(tf.filename, O_PATH);
ASSERT_NE(-1, fd);
int res = fsetxattr(fd, "user.foo", "bar", 4, 0);
#if defined(__BIONIC__)
char buf[10];
ASSERT_EQ(0, res);
ASSERT_EQ(4, fgetxattr(fd, "user.foo", buf, sizeof(buf)));
ASSERT_STREQ("bar", buf);
#else
ASSERT_EQ(-1, res);
ASSERT_EQ(EBADF, errno);
#endif
}
TEST(sys_xattr, fsetxattr_with_opath_toosmall) {
TemporaryFile tf;
int fd = open(tf.filename, O_PATH);
ASSERT_NE(-1, fd);
int res = fsetxattr(fd, "user.foo", "01234567890123456789", 21, 0);
#if defined(__BIONIC__)
char buf[10];
ASSERT_EQ(0, res);
ASSERT_EQ(-1, fgetxattr(fd, "user.foo", buf, sizeof(buf)));
ASSERT_EQ(ERANGE, errno);
#else
ASSERT_EQ(-1, res);
ASSERT_EQ(EBADF, errno);
#endif
}