[PATCH v4 04/22] eal: fix plugin dir walk

[David Marchand]

For '.' and '..' directories (or any short file name),
a out of bound issue occurs.

Caught by UBSan:

EAL: Detected shared linkage of DPDK
../lib/eal/common/eal_common_options.c:420:15: runtime error: index -2
        out of bounds for type 'char[256]'
    #0 0x7f867eedf206 in eal_plugindir_init
        eal_common_options.c
    #1 0x7f867eede58a in eal_plugins_init
        (build/lib/librte_eal.so.25+0xde58a)
        (BuildId: e7e4a1935e4bacb51c82ab1a84098a27decf3b4c)
    #2 0x7f867efb8587 in rte_eal_init
        (build/lib/librte_eal.so.25+0x1b8587)
        (BuildId: e7e4a1935e4bacb51c82ab1a84098a27decf3b4c)
    #3 0x55b62360861e in main
        (/home/runner/work/dpdk/dpdk/build/app/dpdk-testpmd+0x9e061e)
        (BuildId: d821ec918612c83fad8b5ccb6cc518e66bee48cd)
    #4 0x7f8667429d8f in __libc_start_call_main
        csu/../sysdeps/nptl/libc_start_call_main.h:58:16
    #5 0x7f8667429e3f in __libc_start_main
        csu/../csu/libc-start.c:392:3
    #6 0x55b622d9d444 in _start
        (/home/runner/work/dpdk/dpdk/build/app/dpdk-testpmd+0x175444)
        (BuildId: d821ec918612c83fad8b5ccb6cc518e66bee48cd)
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior
        ../lib/eal/common/eal_common_options.c:420:15 in
        ../lib/eal/common/eal_common_options.c:421:15:
        runtime error: index 18446744073709551609 out of bounds
        for type 'char[256]'

Fixes: c57f6e5c604a ("eal: fix plugin loading")
Cc: sta...@dpdk.org

Signed-off-by: David Marchand <david.march...@redhat.com>
Acked-by: Bruce Richardson <bruce.richard...@intel.com>
---
Changes since v2:
- removed check on null termination of dirent,

---
 lib/eal/common/eal_common_options.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/lib/eal/common/eal_common_options.c 
b/lib/eal/common/eal_common_options.c
index f0a9ddeeb7..e6eb04a138 100644
--- a/lib/eal/common/eal_common_options.c
+++ b/lib/eal/common/eal_common_options.c
@@ -399,12 +399,21 @@ eal_plugins_init(void)
 }
 #else
 
+static bool
+ends_with(const char *str, const char *tail)
+{
+       size_t tail_len = strlen(tail);
+       size_t str_len = strlen(str);
+
+       return str_len >= tail_len && strcmp(&str[str_len - tail_len], tail) == 
0;
+}
+
 static int
 eal_plugindir_init(const char *path)
 {
-       DIR *d = NULL;
        struct dirent *dent = NULL;
        char sopath[PATH_MAX];
+       DIR *d = NULL;
 
        if (path == NULL || *path == '\0')
                return 0;
@@ -418,12 +427,8 @@ eal_plugindir_init(const char *path)
 
        while ((dent = readdir(d)) != NULL) {
                struct stat sb;
-               int nlen = strnlen(dent->d_name, sizeof(dent->d_name));
 
-               /* check if name ends in .so or .so.ABI_VERSION */
-               if (strcmp(&dent->d_name[nlen - 3], ".so") != 0 &&
-                   strcmp(&dent->d_name[nlen - 4 - strlen(ABI_VERSION)],
-                          ".so."ABI_VERSION) != 0)
+               if (!ends_with(dent->d_name, ".so") && !ends_with(dent->d_name, 
".so."ABI_VERSION))
                        continue;
 
                snprintf(sopath, sizeof(sopath), "%s/%s", path, dent->d_name);
-- 
2.50.0