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The openat2 syscall was added on Linux 5.6, as an extension of openat. Unlike other open-like functions, the kernel only provides the LFS variant (so files larger than 4GB always succeed, unlike other functions with an offset larger than off_t). Also, similar to other open functions, the new symbol is a cancellable entrypoint. The test case added only stress tests for some of the syscalls' provided functionality, and it is based on an existing kernel self-test. A fortify wrapper is added to verify the argument size if not larger than the current support open_how struct. Gnulib added an openat2 module, which uses read-only for the open_how argument [1]. There is no clear indication whether the kernel will indeed use the argument as in-out, how it would do so, or for which kind of functionality [2]. Also, adding a potentially different prototype than gnulib only would add extra unnecessary friction and extra wrappers to handle it. Checked on x86_64-linux-gnu and aarch64-linux-gnu. [1] https://gitweb.git.savannah.gnu.org/gitweb/?p=gnulib.git;a=commit;h=0b97ffdf32bdab909d02449043447237273df75e [2] https://sourceware.org/pipermail/libc-alpha/2025-September/169740.html Reviewed-by: Carlos O'Donell <carlos@redhat.com>
50 lines
1.8 KiB
C
50 lines
1.8 KiB
C
/* Checking macros for fcntl functions. Linux version.
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Copyright (C) 2025 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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<https://www.gnu.org/licenses/>. */
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#ifndef _FCNTL_H
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# error "Never include <bits/fcntl-linux-fortify.h> directly; use <fcntl.h> instead."
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#endif
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#ifdef __USE_GNU
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extern int __REDIRECT (__openat2_alias, (int __dfd, const char *__filename,
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const struct open_how *__how,
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size_t __usize), openat2)
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__nonnull ((2, 3));
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#if !__fortify_use_clang
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__errordecl (__openat2_invalid_size,
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"the specified size is larger than sizeof (struct open_how)");
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#endif
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__fortify_function int
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openat2 (int __dfd, const char *__filename, const struct open_how *__how,
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size_t __usize)
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__fortify_clang_warning (__builtin_constant_p (__usize)
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&& __usize > sizeof (struct open_how),
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"the specified size is larger than sizeof (struct open_how)")
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{
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#if !__fortify_use_clang
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if (__builtin_constant_p (__usize) && __usize > sizeof (struct open_how))
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__openat2_invalid_size ();
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#endif
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return __openat2_alias (__dfd, __filename, __how, __usize);
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}
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#endif /* use GNU */
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