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    Subject[patch 0/3] [RFC] kernel/glibc mismatch of "readlink" syscall?

    found something which looks for me like a kernel/glibc syscall mismatch. At
    least the parameter list of "readlink" is different in the kernel compared to
    glibc, POSIX and linux-man-pages. I'm not quite sure if this difference was
    intended or not ...

    man 3p readlink:
    ssize_t readlink(const char *restrict path, char *restrict buf, size_t bufsize);
    size_t readlink(const char *restrict path, char *restrict buf, size_t bufsize);

    glibc (/usr/include/unistd.h):
    size_t readlink (__const char *__restrict __path, char *__restrict __buf, size_t

    man 2 readlink:
    ssize_t readlink(const char *path, char *buf, size_t bufsiz);
    asmlinkage long sys_readlink(const char __user *path, char __user *buf, int
    bufsiz); ^^^

    All readlink prototypes, expect the one in the kernel, have an unsigned
    buffer size. Even the readlink(2) man-page, which also describes an error
    statement like this:

    EINVAL bufsiz is not positive.

    Note: the same man-page defined bufsiz as type of size_t (unsigned).

    While reviewing LTP i discovered that the "readlink03" syscall test contains a
    testcase to do a functional error-path test for "EINVAL bufsiz is not positive".
    This testcase is using the glibc readlink() interface, which cause a unsigned
    cast of the value "-1" and let the testcase fail (actually due to gcc/glibc
    fortify checks and cause a __chk_fail()).

    Before workarounding the testcase, or not applying -D_FORTIFY_SOURCE=2 on LTP
    build, i try to understand if there is any reason for this mismatch between
    kernel and glibc/POSIX. Regarding the man-page, i'm quite certain this was a
    copy&paste-error by coping the prototype from the POSIX man-page.

    Even sys_readlinkat(), which got introduced a long time after sys_readlink(),
    got a signed buffer size. Intended?

    In the rare case all this was unintended, find patches for kernel, man-pages
    and LTP to change the kernel readlink syscall interface to a unsigned buffer


    best regards,

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      Last update: 2008-10-23 17:09    [W:0.024 / U:33.860 seconds]
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