[Xen-changelog] [xen stable-4.6] libfsimage: replace deprecated readdir_r() with readdir()

[patchbot@xxxxxxx]

commit a819871f443f49bff822ae1bcf02dbc327c2aace
Author:     Chris Patterson <pattersonc@xxxxxxxxxxxx>
AuthorDate: Fri Jun 3 12:50:10 2016 -0400
Commit:     Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
CommitDate: Wed May 29 12:03:23 2019 +0100

    libfsimage: replace deprecated readdir_r() with readdir()
    
    Replace the usage of readdir_r() with readdir() to address a
    compilation error under glibc due to the deprecation of readdir_r
    for their next release (2.24) [1, 2].
    
    Add new error checking on readdir(), and fail if error occurs.
    
    --
    
    From the GNU libc manual [3]:
    "
     It is expected that future versions of POSIX will obsolete readdir_r and
     mandate the level of thread safety for readdir which is provided by the
     GNU C Library and other implementations today.
    "
    
    There is a filed bug in the Austin Group Defect Tracker [4]  in which 
'dalias'
    proposes (in comment 0001632) that:
    "
       I would like to propose an alternate solution. For readdir, replace the 
text:
        "The readdir() function need not be thread-safe."
       with:
        "If multiple threads call the readdir() function with the same directory
        stream argument and without synchronization to preclude simultaneous
        access, then the behavior is undefined."
    
       With this change, the clunky readdir_r function is no longer needed or
       useful, and should probably be deprecated. As the only reasonable way
       to meet the implementation requirements for readdir is to have the dirent
       buffer in the DIR structure, this change should not require any change to
       existing implementations.
    "
    
    [1] https://sourceware.org/ml/libc-alpha/2016-02/msg00093.html
    [2] https://sourceware.org/bugzilla/show_bug.cgi?id=19056
    [3] 
https://www.gnu.org/software/libc/manual/html_node/Reading_002fClosing-Directory.html
    [4] http://austingroupbugs.net/view.php?id=696
    
    Signed-off-by: Chris Patterson <pattersonc@xxxxxxxxxxxx>
    Acked-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
    Release-acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>
    (cherry picked from commit c2a17869d5dcd845d646bf4db122cad73596a2be)
---
 tools/libfsimage/common/fsimage_plugin.c | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/tools/libfsimage/common/fsimage_plugin.c 
b/tools/libfsimage/common/fsimage_plugin.c
index 3fa06c785c..0744e7b3ca 100644
--- a/tools/libfsimage/common/fsimage_plugin.c
+++ b/tools/libfsimage/common/fsimage_plugin.c
@@ -123,7 +123,6 @@ static int load_plugins(void)
 {
        const char *fsdir = getenv("FSIMAGE_FSDIR");
        struct dirent *dp = NULL;
-       struct dirent *dpp;
        DIR *dir = NULL;
        char *tmp = NULL;
        size_t name_max;
@@ -139,22 +138,26 @@ static int load_plugins(void)
        if ((tmp = malloc(name_max + 1)) == NULL)
                goto fail;
 
-       if ((dp = malloc(sizeof (struct dirent) + name_max + 1)) == NULL)
-               goto fail;
-
        if ((dir = opendir(fsdir)) == NULL)
                goto fail;
 
-       bzero(dp, sizeof (struct dirent) + name_max + 1);
+       for (;;) {
+               errno = 0;
+               dp = readdir(dir);
+
+               if (dp == NULL && errno != 0)
+                       goto fail;
+
+               if (dp == NULL)
+                       break;
 
-       while (readdir_r(dir, dp, &dpp) == 0 && dpp != NULL) {
-               if (strcmp(dpp->d_name, ".") == 0)
+               if (strcmp(dp->d_name, ".") == 0)
                        continue;
-               if (strcmp(dpp->d_name, "..") == 0)
+               if (strcmp(dp->d_name, "..") == 0)
                        continue;
 
                (void) snprintf(tmp, name_max, "%s/%s/fsimage.so", fsdir,
-                       dpp->d_name);
+                       dp->d_name);
 
                if (init_plugin(tmp) != 0)
                        goto fail;
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.6

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