From 3cbc6c627fe57c9a9783c52d148078f8d52f7b96 Mon Sep 17 00:00:00 2001 From: Nick Kralevich Date: Sat, 31 Jan 2015 19:57:46 -0800 Subject: [PATCH] Add fchmodat(AT_SYMLINK_NOFOLLOW) and fchmod O_PATH support Many libc functions have an option to not follow symbolic links. This is useful to avoid security sensitive code from inadvertantly following attacker supplied symlinks and taking inappropriate action on files it shouldn't. For example, open() has O_NOFOLLOW, chown() has lchown(), stat() has lstat(), etc. There is no such equivalent function for chmod(), such as lchmod(). To address this, POSIX introduced fchmodat(AT_SYMLINK_NOFOLLOW), which is intended to provide a way to perform a chmod operation which doesn't follow symlinks. Currently, the Linux kernel doesn't implement AT_SYMLINK_NOFOLLOW. In GLIBC, attempting to use the AT_SYMLINK_NOFOLLOW flag causes fchmodat to return ENOTSUP. Details are in "man fchmodat". Bionic currently differs from GLIBC in that AT_SYMLINK_NOFOLLOW is silently ignored and treated as if the flag wasn't present. This patch provides a userspace implementation of AT_SYMLINK_NOFOLLOW for bionic. Using open(O_PATH | O_NOFOLLOW), we can provide a way to atomically change the permissions on files without worrying about race conditions. As part of this change, we add support for fchmod on O_PATH file descriptors, because it's relatively straight forward and could be useful in the future. The basic idea behind this implementation comes from https://sourceware.org/bugzilla/show_bug.cgi?id=14578 , specifically comment #10. Change-Id: I1eba0cdb2c509d9193ceecf28f13118188a3cfa7 --- libc/Android.mk | 2 + libc/SYSCALLS.TXT | 4 +- .../syscalls/{fchmod.S => __fchmod.S} | 4 +- .../syscalls/{fchmodat.S => __fchmodat.S} | 4 +- .../syscalls/{fchmod.S => __fchmod.S} | 5 +- .../syscalls/{fchmodat.S => __fchmodat.S} | 5 +- .../syscalls/{fchmod.S => __fchmod.S} | 4 +- .../syscalls/{fchmodat.S => __fchmodat.S} | 4 +- .../syscalls/{fchmod.S => __fchmod.S} | 5 +- .../syscalls/{fchmodat.S => __fchmodat.S} | 5 +- .../syscalls/{fchmod.S => __fchmod.S} | 4 +- .../syscalls/{fchmodat.S => __fchmodat.S} | 15 +-- .../syscalls/{fchmod.S => __fchmod.S} | 5 +- .../syscalls/{fchmodat.S => __fchmodat.S} | 6 +- libc/bionic/fchmod.cpp | 72 ++++++++++ libc/bionic/fchmodat.cpp | 67 ++++++++++ tests/sys_stat_test.cpp | 124 ++++++++++++++++++ 17 files changed, 300 insertions(+), 35 deletions(-) rename libc/arch-arm/syscalls/{fchmod.S => __fchmod.S} (89%) rename libc/arch-arm/syscalls/{fchmodat.S => __fchmodat.S} (88%) rename libc/arch-arm64/syscalls/{fchmod.S => __fchmod.S} (82%) rename libc/arch-arm64/syscalls/{fchmodat.S => __fchmodat.S} (81%) rename libc/arch-mips/syscalls/{fchmod.S => __fchmod.S} (89%) rename libc/arch-mips/syscalls/{fchmodat.S => __fchmodat.S} (88%) rename libc/arch-mips64/syscalls/{fchmod.S => __fchmod.S} (88%) rename libc/arch-mips64/syscalls/{fchmodat.S => __fchmodat.S} (86%) rename libc/arch-x86/syscalls/{fchmod.S => __fchmod.S} (94%) rename libc/arch-x86/syscalls/{fchmodat.S => __fchmodat.S} (70%) rename libc/arch-x86_64/syscalls/{fchmod.S => __fchmod.S} (84%) rename libc/arch-x86_64/syscalls/{fchmodat.S => __fchmodat.S} (82%) create mode 100644 libc/bionic/fchmod.cpp create mode 100644 libc/bionic/fchmodat.cpp diff --git a/libc/Android.mk b/libc/Android.mk index 691017a8b..9c54ab865 100644 --- a/libc/Android.mk +++ b/libc/Android.mk @@ -115,6 +115,8 @@ libc_bionic_src_files := \ bionic/error.cpp \ bionic/eventfd_read.cpp \ bionic/eventfd_write.cpp \ + bionic/fchmod.cpp \ + bionic/fchmodat.cpp \ bionic/ffs.cpp \ bionic/flockfile.cpp \ bionic/fork.cpp \ diff --git a/libc/SYSCALLS.TXT b/libc/SYSCALLS.TXT index 0fa2a1e10..d68a00fd1 100644 --- a/libc/SYSCALLS.TXT +++ b/libc/SYSCALLS.TXT @@ -113,7 +113,7 @@ int writev(int, const struct iovec*, int) all int __fcntl64:fcntl64(int, int, void*) arm,mips,x86 int fcntl(int, int, void*) arm64,mips64,x86_64 int flock(int, int) all -int fchmod(int, mode_t) all +int __fchmod:fchmod(int, mode_t) all int dup(int) all int pipe2(int*, int) all int dup3(int, int, int) all @@ -131,7 +131,7 @@ int __getdents64:getdents64(unsigned int, struct dirent*, unsigned int) arm,ar int __openat:openat(int, const char*, int, mode_t) all int faccessat(int, const char*, int, int) all -int fchmodat(int, const char*, mode_t, int) all +int __fchmodat:fchmodat(int, const char*, mode_t) all int fchownat(int, const char*, uid_t, gid_t, int) all int fstatat64|fstatat:fstatat64(int, const char*, struct stat*, int) arm,mips,x86 int fstatat64|fstatat:newfstatat(int, const char*, struct stat*, int) arm64,x86_64 diff --git a/libc/arch-arm/syscalls/fchmod.S b/libc/arch-arm/syscalls/__fchmod.S similarity index 89% rename from libc/arch-arm/syscalls/fchmod.S rename to libc/arch-arm/syscalls/__fchmod.S index 5675f0a33..ff888a17e 100644 --- a/libc/arch-arm/syscalls/fchmod.S +++ b/libc/arch-arm/syscalls/__fchmod.S @@ -2,7 +2,7 @@ #include -ENTRY(fchmod) +ENTRY(__fchmod) mov ip, r7 ldr r7, =__NR_fchmod swi #0 @@ -11,4 +11,4 @@ ENTRY(fchmod) bxls lr neg r0, r0 b __set_errno_internal -END(fchmod) +END(__fchmod) diff --git a/libc/arch-arm/syscalls/fchmodat.S b/libc/arch-arm/syscalls/__fchmodat.S similarity index 88% rename from libc/arch-arm/syscalls/fchmodat.S rename to libc/arch-arm/syscalls/__fchmodat.S index 3f7e0ee24..4d10f00b8 100644 --- a/libc/arch-arm/syscalls/fchmodat.S +++ b/libc/arch-arm/syscalls/__fchmodat.S @@ -2,7 +2,7 @@ #include -ENTRY(fchmodat) +ENTRY(__fchmodat) mov ip, r7 ldr r7, =__NR_fchmodat swi #0 @@ -11,4 +11,4 @@ ENTRY(fchmodat) bxls lr neg r0, r0 b __set_errno_internal -END(fchmodat) +END(__fchmodat) diff --git a/libc/arch-arm64/syscalls/fchmod.S b/libc/arch-arm64/syscalls/__fchmod.S similarity index 82% rename from libc/arch-arm64/syscalls/fchmod.S rename to libc/arch-arm64/syscalls/__fchmod.S index 83a80607d..05c67fc37 100644 --- a/libc/arch-arm64/syscalls/fchmod.S +++ b/libc/arch-arm64/syscalls/__fchmod.S @@ -2,7 +2,7 @@ #include -ENTRY(fchmod) +ENTRY(__fchmod) mov x8, __NR_fchmod svc #0 @@ -11,4 +11,5 @@ ENTRY(fchmod) b.hi __set_errno_internal ret -END(fchmod) +END(__fchmod) +.hidden __fchmod diff --git a/libc/arch-arm64/syscalls/fchmodat.S b/libc/arch-arm64/syscalls/__fchmodat.S similarity index 81% rename from libc/arch-arm64/syscalls/fchmodat.S rename to libc/arch-arm64/syscalls/__fchmodat.S index 8c5bb0e13..2406ea8e3 100644 --- a/libc/arch-arm64/syscalls/fchmodat.S +++ b/libc/arch-arm64/syscalls/__fchmodat.S @@ -2,7 +2,7 @@ #include -ENTRY(fchmodat) +ENTRY(__fchmodat) mov x8, __NR_fchmodat svc #0 @@ -11,4 +11,5 @@ ENTRY(fchmodat) b.hi __set_errno_internal ret -END(fchmodat) +END(__fchmodat) +.hidden __fchmodat diff --git a/libc/arch-mips/syscalls/fchmod.S b/libc/arch-mips/syscalls/__fchmod.S similarity index 89% rename from libc/arch-mips/syscalls/fchmod.S rename to libc/arch-mips/syscalls/__fchmod.S index 2a95cc30d..9bc491c21 100644 --- a/libc/arch-mips/syscalls/fchmod.S +++ b/libc/arch-mips/syscalls/__fchmod.S @@ -2,7 +2,7 @@ #include -ENTRY(fchmod) +ENTRY(__fchmod) .set noreorder .cpload t9 li v0, __NR_fchmod @@ -16,4 +16,4 @@ ENTRY(fchmod) j t9 nop .set reorder -END(fchmod) +END(__fchmod) diff --git a/libc/arch-mips/syscalls/fchmodat.S b/libc/arch-mips/syscalls/__fchmodat.S similarity index 88% rename from libc/arch-mips/syscalls/fchmodat.S rename to libc/arch-mips/syscalls/__fchmodat.S index d9de036dd..07ea8f8b3 100644 --- a/libc/arch-mips/syscalls/fchmodat.S +++ b/libc/arch-mips/syscalls/__fchmodat.S @@ -2,7 +2,7 @@ #include -ENTRY(fchmodat) +ENTRY(__fchmodat) .set noreorder .cpload t9 li v0, __NR_fchmodat @@ -16,4 +16,4 @@ ENTRY(fchmodat) j t9 nop .set reorder -END(fchmodat) +END(__fchmodat) diff --git a/libc/arch-mips64/syscalls/fchmod.S b/libc/arch-mips64/syscalls/__fchmod.S similarity index 88% rename from libc/arch-mips64/syscalls/fchmod.S rename to libc/arch-mips64/syscalls/__fchmod.S index a877b781f..94dd0a1e7 100644 --- a/libc/arch-mips64/syscalls/fchmod.S +++ b/libc/arch-mips64/syscalls/__fchmod.S @@ -2,7 +2,7 @@ #include -ENTRY(fchmod) +ENTRY(__fchmod) .set push .set noreorder li v0, __NR_fchmod @@ -22,4 +22,5 @@ ENTRY(fchmod) j t9 move ra, t0 .set pop -END(fchmod) +END(__fchmod) +.hidden __fchmod diff --git a/libc/arch-mips64/syscalls/fchmodat.S b/libc/arch-mips64/syscalls/__fchmodat.S similarity index 86% rename from libc/arch-mips64/syscalls/fchmodat.S rename to libc/arch-mips64/syscalls/__fchmodat.S index 151492aa7..79f453f4c 100644 --- a/libc/arch-mips64/syscalls/fchmodat.S +++ b/libc/arch-mips64/syscalls/__fchmodat.S @@ -2,7 +2,7 @@ #include -ENTRY(fchmodat) +ENTRY(__fchmodat) .set push .set noreorder li v0, __NR_fchmodat @@ -22,4 +22,5 @@ ENTRY(fchmodat) j t9 move ra, t0 .set pop -END(fchmodat) +END(__fchmodat) +.hidden __fchmodat diff --git a/libc/arch-x86/syscalls/fchmod.S b/libc/arch-x86/syscalls/__fchmod.S similarity index 94% rename from libc/arch-x86/syscalls/fchmod.S rename to libc/arch-x86/syscalls/__fchmod.S index 37851ff47..7ad213e7e 100644 --- a/libc/arch-x86/syscalls/fchmod.S +++ b/libc/arch-x86/syscalls/__fchmod.S @@ -2,7 +2,7 @@ #include -ENTRY(fchmod) +ENTRY(__fchmod) pushl %ebx .cfi_def_cfa_offset 8 .cfi_rel_offset ebx, 0 @@ -23,4 +23,4 @@ ENTRY(fchmod) popl %ecx popl %ebx ret -END(fchmod) +END(__fchmod) diff --git a/libc/arch-x86/syscalls/fchmodat.S b/libc/arch-x86/syscalls/__fchmodat.S similarity index 70% rename from libc/arch-x86/syscalls/fchmodat.S rename to libc/arch-x86/syscalls/__fchmodat.S index f5155120d..f03c03f41 100644 --- a/libc/arch-x86/syscalls/fchmodat.S +++ b/libc/arch-x86/syscalls/__fchmodat.S @@ -2,7 +2,7 @@ #include -ENTRY(fchmodat) +ENTRY(__fchmodat) pushl %ebx .cfi_def_cfa_offset 8 .cfi_rel_offset ebx, 0 @@ -12,13 +12,9 @@ ENTRY(fchmodat) pushl %edx .cfi_adjust_cfa_offset 4 .cfi_rel_offset edx, 0 - pushl %esi - .cfi_adjust_cfa_offset 4 - .cfi_rel_offset esi, 0 - mov 20(%esp), %ebx - mov 24(%esp), %ecx - mov 28(%esp), %edx - mov 32(%esp), %esi + mov 16(%esp), %ebx + mov 20(%esp), %ecx + mov 24(%esp), %edx movl $__NR_fchmodat, %eax int $0x80 cmpl $-MAX_ERRNO, %eax @@ -28,9 +24,8 @@ ENTRY(fchmodat) call __set_errno_internal addl $4, %esp 1: - popl %esi popl %edx popl %ecx popl %ebx ret -END(fchmodat) +END(__fchmodat) diff --git a/libc/arch-x86_64/syscalls/fchmod.S b/libc/arch-x86_64/syscalls/__fchmod.S similarity index 84% rename from libc/arch-x86_64/syscalls/fchmod.S rename to libc/arch-x86_64/syscalls/__fchmod.S index b35bd21ac..ba75f7487 100644 --- a/libc/arch-x86_64/syscalls/fchmod.S +++ b/libc/arch-x86_64/syscalls/__fchmod.S @@ -2,7 +2,7 @@ #include -ENTRY(fchmod) +ENTRY(__fchmod) movl $__NR_fchmod, %eax syscall cmpq $-MAX_ERRNO, %rax @@ -12,4 +12,5 @@ ENTRY(fchmod) call __set_errno_internal 1: ret -END(fchmod) +END(__fchmod) +.hidden __fchmod diff --git a/libc/arch-x86_64/syscalls/fchmodat.S b/libc/arch-x86_64/syscalls/__fchmodat.S similarity index 82% rename from libc/arch-x86_64/syscalls/fchmodat.S rename to libc/arch-x86_64/syscalls/__fchmodat.S index 2d78d8e81..a8fae9525 100644 --- a/libc/arch-x86_64/syscalls/fchmodat.S +++ b/libc/arch-x86_64/syscalls/__fchmodat.S @@ -2,8 +2,7 @@ #include -ENTRY(fchmodat) - movq %rcx, %r10 +ENTRY(__fchmodat) movl $__NR_fchmodat, %eax syscall cmpq $-MAX_ERRNO, %rax @@ -13,4 +12,5 @@ ENTRY(fchmodat) call __set_errno_internal 1: ret -END(fchmodat) +END(__fchmodat) +.hidden __fchmodat diff --git a/libc/bionic/fchmod.cpp b/libc/bionic/fchmod.cpp new file mode 100644 index 000000000..6e020b6be --- /dev/null +++ b/libc/bionic/fchmod.cpp @@ -0,0 +1,72 @@ +/* + * 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 +#include +#include +#include +#include +#include + +extern "C" int __fchmod(int, mode_t); + +int fchmod(int fd, mode_t mode) { + int saved_errno = errno; + int result = __fchmod(fd, mode); + + if ((result == 0) || (errno != EBADF)) { + return result; + } + + // fd could be an O_PATH file descriptor, and the kernel + // may not directly support fchmod() on such a file descriptor. + // Use /proc/self/fd instead to emulate this support. + // https://sourceware.org/bugzilla/show_bug.cgi?id=14578 + // + // As of February 2015, there are no kernels which support fchmod + // on an O_PATH file descriptor, and "man open" documents fchmod + // on O_PATH file descriptors as returning EBADF. + 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; + result = chmod(buf, mode); + if ((result == -1) && (errno == ELOOP)) { + // Linux does not support changing the mode of a symlink. + // For fchmodat(AT_SYMLINK_NOFOLLOW), POSIX requires a return + // value of ENOTSUP. Assume that's true here too. + errno = ENOTSUP; + } + + return result; +} diff --git a/libc/bionic/fchmodat.cpp b/libc/bionic/fchmodat.cpp new file mode 100644 index 000000000..c28e15ac7 --- /dev/null +++ b/libc/bionic/fchmodat.cpp @@ -0,0 +1,67 @@ +/* + * 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 +#include +#include +#include +#include + +#include "private/ErrnoRestorer.h" + +extern "C" int __fchmodat(int, const char*, mode_t); + +int fchmodat(int dirfd, const char* pathname, mode_t mode, int flags) { + if ((flags & ~AT_SYMLINK_NOFOLLOW) != 0) { + errno = EINVAL; + return -1; + } + + if (flags & AT_SYMLINK_NOFOLLOW) { + // Emulate AT_SYMLINK_NOFOLLOW using the mechanism described + // at https://sourceware.org/bugzilla/show_bug.cgi?id=14578 + // comment #10 + + int fd = openat(dirfd, pathname, O_PATH | O_NOFOLLOW | O_CLOEXEC); + if (fd == -1) { + return -1; // returns errno from openat + } + + // POSIX requires that ENOTSUP be returned when the system + // doesn't support setting the mode of a symbolic link. + // This is true for all Linux kernels. + // We rely on the O_PATH compatibility layer added in the + // fchmod() function to get errno correct. + int result = fchmod(fd, mode); + ErrnoRestorer errno_restorer; // don't let close() clobber errno + close(fd); + return result; + } + + return __fchmodat(dirfd, pathname, mode); +} diff --git a/tests/sys_stat_test.cpp b/tests/sys_stat_test.cpp index e46577469..7bbb7c665 100644 --- a/tests/sys_stat_test.cpp +++ b/tests/sys_stat_test.cpp @@ -95,3 +95,127 @@ TEST(sys_stat, stat64_lstat64_fstat64) { ASSERT_EQ(0, fstat64(fd, &sb)); close(fd); } + +TEST(sys_stat, fchmodat_EFAULT_file) { + ASSERT_EQ(-1, fchmodat(AT_FDCWD, (char *) 0x1, 0751, 0)); + ASSERT_EQ(EFAULT, errno); +} + +TEST(sys_stat, fchmodat_AT_SYMLINK_NOFOLLOW_EFAULT_file) { + ASSERT_EQ(-1, fchmodat(AT_FDCWD, (char *) 0x1, 0751, AT_SYMLINK_NOFOLLOW)); +#if defined(__BIONIC__) + ASSERT_EQ(EFAULT, errno); +#else + // glibc 2.19 does not implement AT_SYMLINK_NOFOLLOW and always + // returns ENOTSUP + ASSERT_EQ(ENOTSUP, errno); +#endif +} + +TEST(sys_stat, fchmodat_bad_flags) { + ASSERT_EQ(-1, fchmodat(AT_FDCWD, "/blah", 0751, ~AT_SYMLINK_NOFOLLOW)); + ASSERT_EQ(EINVAL, errno); +} + +TEST(sys_stat, fchmodat_bad_flags_ALL) { + ASSERT_EQ(-1, fchmodat(AT_FDCWD, "/blah", 0751, ~0)); + ASSERT_EQ(EINVAL, errno); +} + +TEST(sys_stat, fchmodat_nonexistant_file) { + ASSERT_EQ(-1, fchmodat(AT_FDCWD, "/blah", 0751, 0)); + ASSERT_EQ(ENOENT, errno); +} + +TEST(sys_stat, fchmodat_AT_SYMLINK_NOFOLLOW_nonexistant_file) { + ASSERT_EQ(-1, fchmodat(AT_FDCWD, "/blah", 0751, AT_SYMLINK_NOFOLLOW)); +#if defined(__BIONIC__) + ASSERT_EQ(ENOENT, errno); +#else + // glibc 2.19 does not implement AT_SYMLINK_NOFOLLOW and always + // returns ENOTSUP + ASSERT_EQ(ENOTSUP, errno); +#endif +} + +TEST(sys_stat, fchmodat_file) { + TemporaryFile tf; + struct stat sb; + + ASSERT_EQ(0, fchmodat(AT_FDCWD, tf.filename, 0751, 0)); + ASSERT_EQ(0, fstat(tf.fd, &sb)); + ASSERT_TRUE(0751 == (sb.st_mode & (S_IRWXU | S_IRWXG | S_IRWXO))); +} + +TEST(sys_stat, fchmodat_AT_SYMLINK_NOFOLLOW_file) { + TemporaryFile tf; + errno = 0; + int result = fchmodat(AT_FDCWD, tf.filename, 0751, AT_SYMLINK_NOFOLLOW); + +#if defined(__BIONIC__) + struct stat sb; + ASSERT_EQ(0, result); + ASSERT_EQ(0, errno); + ASSERT_EQ(0, fstat(tf.fd, &sb)); + ASSERT_TRUE(0751 == (sb.st_mode & (S_IRWXU | S_IRWXG | S_IRWXO))); +#else + // glibc 2.19 does not implement AT_SYMLINK_NOFOLLOW and always + // returns ENOTSUP + ASSERT_EQ(-1, result); + ASSERT_EQ(ENOTSUP, errno); +#endif +} + +TEST(sys_stat, fchmodat_symlink) { + TemporaryFile tf; + char linkname[255]; + struct stat sb; + + snprintf(linkname, sizeof(linkname), "%s.link", tf.filename); + + ASSERT_EQ(0, symlink(tf.filename, linkname)); + ASSERT_EQ(0, fchmodat(AT_FDCWD, linkname, 0751, 0)); + ASSERT_EQ(0, fstat(tf.fd, &sb)); + ASSERT_TRUE(0751 == (sb.st_mode & (S_IRWXU | S_IRWXG | S_IRWXO))); + unlink(linkname); +} + +TEST(sys_stat, fchmodat_dangling_symlink) { + TemporaryFile tf; + char linkname[255]; + char target[255]; + + snprintf(linkname, sizeof(linkname), "%s.link", tf.filename); + snprintf(target, sizeof(target), "%s.doesnotexist", tf.filename); + + ASSERT_EQ(0, symlink(target, linkname)); + ASSERT_EQ(-1, fchmodat(AT_FDCWD, linkname, 0751, 0)); + ASSERT_EQ(ENOENT, errno); + unlink(linkname); +} + +TEST(sys_stat, fchmodat_AT_SYMLINK_NOFOLLOW_with_symlink) { + TemporaryFile tf; + char linkname[255]; + + snprintf(linkname, sizeof(linkname), "%s.link", tf.filename); + + ASSERT_EQ(0, symlink(tf.filename, linkname)); + ASSERT_EQ(-1, fchmodat(AT_FDCWD, linkname, 0751, AT_SYMLINK_NOFOLLOW)); + ASSERT_EQ(ENOTSUP, errno); + unlink(linkname); +} + +TEST(sys_stat, fchmodat_AT_SYMLINK_NOFOLLOW_with_dangling_symlink) { + TemporaryFile tf; + char linkname[255]; + char target[255]; + + snprintf(linkname, sizeof(linkname), "%s.link", tf.filename); + snprintf(target, sizeof(target), "%s.doesnotexist", tf.filename); + + ASSERT_EQ(0, symlink(target, linkname)); + ASSERT_EQ(-1, fchmodat(AT_FDCWD, linkname, 0751, AT_SYMLINK_NOFOLLOW)); + ASSERT_EQ(ENOTSUP, errno); + unlink(linkname); +}