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Peter Griffin
406c706c7b
vfs: vfs_tmpfile: ensure O_EXCL flag is enforced
If O_EXCL is *not* specified, then linkat() can be used to link the temporary file into the filesystem. If O_EXCL is specified then linkat() should fail (-1). After commit 863f144f12ad ("vfs: open inside ->tmpfile()") the O_EXCL flag is no longer honored by the vfs layer for tmpfile, which means the file can be linked even if O_EXCL flag is specified, which is a change in behaviour for userspace! The open flags was previously passed as a parameter, so it was uneffected by the changes to file->f_flags caused by finish_open(). This patch fixes the issue by storing file->f_flags in a local variable so the O_EXCL test logic is restored. This regression was detected by Android CTS Bionic fcntl() tests running on android-mainline [1]. [1] https://android.googlesource.com/platform/bionic/+/ refs/heads/master/tests/fcntl_test.cpp#352 Fixes: 863f144f12ad ("vfs: open inside ->tmpfile()") Acked-by: Miklos Szeredi <mszeredi@redhat.com> Tested-by: Will McVicker <willmcvicker@google.com> Signed-off-by: Peter Griffin <peter.griffin@linaro.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Linux kernel ============ There are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. Please read Documentation/admin-guide/README.rst first. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. The formatted documentation can also be read online at: https://www.kernel.org/doc/html/latest/ There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.
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