On Tue, Dec 15, 2009 at 08:32:49AM +0100, Jim Meyering wrote:
> Without this patch, virFileResolveLink could misbehave
> when applied to a file on a POSIX-nonconforming file system.
>
> The fix is to use gnulib's areadlink module, but it's GPL'd.
> I'm ready to relax it to LGPLv2+, and have asked the other author
> for his rubber stamp. Once that's fixed, this change will depend
> on having an up-to-date gnulib submodule. That will be the subject of
> my next message.
>
> >From a3133b2e8b1453578b30e4b9c83c7473feb7c65b Mon Sep 17 00:00:00 2001
> From: Jim Meyering <meyering@xxxxxxxxxx>
> Date: Tue, 15 Dec 2009 08:27:53 +0100
> Subject: [PATCH] avoid malfunction when virFileResolveLink is applied to non-POSIX FS
>
> The virFileResolveLink utility function relied on the POSIX guarantee
> that stat.st_size of a symlink is the length of the value. However,
> on some types of file systems, it is invalid, so do not rely on it.
> Use gnulib's areadlink module instead.
> * bootstrap (modules): Add areadlink.
> * src/util/util.c: Include "areadlink.h".
> Let areadlink perform the readlink and malloc.
> * configure.in (AC_CHECK_FUNCS): Remove readlink. No need,
> since it's presence is guaranteed by gnulib.
> ---
> bootstrap | 1 +
> configure.in | 2 +-
> src/util/util.c | 27 +++------------------------
> 3 files changed, 5 insertions(+), 25 deletions(-)
>
> diff --git a/bootstrap b/bootstrap
> index 667af4f..c07d851 100755
> --- a/bootstrap
> +++ b/bootstrap
> @@ -65,6 +65,7 @@ gnulib_tool=$GNULIB_SRCDIR/gnulib-tool
> <$gnulib_tool || exit
>
> modules='
> +areadlink
> base64
> c-ctype
> close
> diff --git a/configure.in b/configure.in
> index 6135932..6ed2efd 100644
> --- a/configure.in
> +++ b/configure.in
> @@ -83,7 +83,7 @@ dnl Use --disable-largefile if you don't want this.
> AC_SYS_LARGEFILE
>
> dnl Availability of various common functions (non-fatal if missing).
> -AC_CHECK_FUNCS([cfmakeraw regexec uname sched_getaffinity getuid getgid posix_fallocate mmap readlink])
> +AC_CHECK_FUNCS([cfmakeraw regexec uname sched_getaffinity getuid getgid posix_fallocate mmap])
>
> dnl Availability of various not common threadsafe functions
> AC_CHECK_FUNCS([strerror_r strtok_r getmntent_r getgrnam_r getpwuid_r])
> diff --git a/src/util/util.c b/src/util/util.c
> index 694838a..44a4b2f 100644
> --- a/src/util/util.c
> +++ b/src/util/util.c
> @@ -64,6 +64,7 @@
> #include <mntent.h>
> #endif
>
> +#include "areadlink.h"
> #include "virterror_internal.h"
> #include "logging.h"
> #include "event.h"
> @@ -1059,10 +1060,7 @@ int virFileLinkPointsTo(const char *checkLink,
> int virFileResolveLink(const char *linkpath,
> char **resultpath)
> {
> -#ifdef HAVE_READLINK
> struct stat st;
> - char *buf;
> - int n;
>
> *resultpath = NULL;
>
> @@ -1075,28 +1073,9 @@ int virFileResolveLink(const char *linkpath,
> return 0;
> }
>
> - /* Posix says that 'st_size' field from
> - * result of an lstat() call is filled with
> - * number of bytes in the destination
> - * filename.
> - */
> - if (VIR_ALLOC_N(buf, st.st_size + 1) < 0)
> - return -ENOMEM;
> -
> - if ((n = readlink(linkpath, buf, st.st_size)) < 0) {
> - VIR_FREE(buf);
> - return -errno;
> - }
> -
> - buf[n] = '\0';
> + *resultpath = areadlink (linkpath);
>
> - *resultpath = buf;
> - return 0;
> -#else
> - if (!(*resultpath = strdup(linkpath)))
> - return -ENOMEM;
> - return 0;
> -#endif
> + return *resultpath == NULL ? -1 : 0;
> }
>
> /*
ACK
Daniel
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