Messages in this thread | | | Date | Thu, 23 Oct 2008 16:50:55 +0200 | From | Daniel Gollub <> | Subject | [patch 0/3] [RFC] kernel/glibc mismatch of "readlink" syscall? |
| |
Hi,
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);
http://www.opengroup.org/onlinepubs/000095399/functions/readlink.html: 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); ^^^^^^ linux-2.6/include/linux/syscalls.h: 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 size.
Thoughts?
best regards, Daniel
| |