ucm: fix TOCTOU race condition #367
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Separately checking the state of a file before operating on it may allow an attacker to modify the file between the two operations. Fix by calling readlink first. If that fails, then path should not be a symbolic link and we call open() followed by fstat(). open() with O_NOFOLLOW will return an error if the file is a symlink. Signed-off-by: Mingjie Shen <[email protected]>
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Separately checking the state of a file before operating on it may allow an attacker to modify the file between the two operations. Fix by calling readlink first. If that fails, then path should not be a symbolic link and we call open() followed by fstat(). open() with O_NOFOLLOW will return an error if the file is a symlink.