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lsof: correct check for symbolic link

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Busybox lsof used the d_type field of a 'struct dirent' to verify whether the
entry is a symbolic link. This field, however, is not portable. On at least
one board [1] I have seen, that field is 0, and the check fails even though
the entry is a link.

The explicit check for a symbolic link is really only needed to skip the
default directory entries '.' and '..'. The directory /proc/<pid>/fd/
should not contain anything else but these two and symbolic links.
With these assumptions, this patch replaces the explicit link check with a
basic check for '.' and '..' (and any hidden file). In the unlikely case that
there are other file types, xmalloc_readlink() will return NULL, and we can
skip the entry.

[1] A MIPS-based board with glibc 2.9, Linux 2.6.32.27.

Signed-off-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Thomas De Schampheleire 2013-06-21 21:27:56 +02:00 committed by Denys Vlasenko
parent d66eb9042d
commit 879f008a8f
1 changed files with 6 additions and 3 deletions
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9
procps/lsof.c
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@ -61,9 +61,12 @@ int lsof_main(int argc UNUSED_PARAM, char **argv UNUSED_PARAM)
d_fd = opendir(name);
if (d_fd) {
while ((entry = readdir(d_fd)) != NULL) {
if (entry->d_type == DT_LNK) {
safe_strncpy(name + baseofs, entry->d_name, 10);
fdlink = xmalloc_readlink(name);
/* Skip entries '.' and '..' (and any hidden file) */
if (entry->d_name[0] == '.')
continue;
safe_strncpy(name + baseofs, entry->d_name, 10);
if ((fdlink = xmalloc_readlink(name)) != NULL) {
printf("%d\t%s\t%s\n", proc->pid, proc->exe, fdlink);
free(fdlink);
}