52a713fdd0
Currently getcwd(3) can succeed without returning an absolute path because the underlying getcwd syscall, starting with linux commit v2.6.36-rc1~96^2~2, may succeed without returning an absolute path. This is a conformance issue because "The getcwd() function shall place an absolute pathname of the current working directory in the array pointed to by buf, and return buf". This is also a security issue because a non-absolute path returned by getcwd(3) causes a buffer underflow in realpath(3). Fix this by checking the path returned by getcwd syscall and falling back to generic_getcwd if the path is not absolute, effectively making getcwd(3) fail with ENOENT. The error code is chosen for consistency with the case when the current directory is unlinked. [BZ #22679] CVE-2018-1000001 * sysdeps/unix/sysv/linux/getcwd.c (__getcwd): Fall back to generic_getcwd if the path returned by getcwd syscall is not absolute. * io/tst-getcwd-abspath.c: New test. * io/Makefile (tests): Add tst-getcwd-abspath.
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