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fail fdopendir for O_PATH file descriptors

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fdopendir is specified to fail with EBADF if the file descriptor
passed is not open for reading. while O_PATH is an extension and
arguably exempt from this requirement, it's used, albeit incompletely,
to implement O_SEARCH, and fdopendir should fail when passed an
O_SEARCH file descriptor.

the new check is performed after fstat so that we don't have to
consider the possibility that the fd is invalid.

an alternate solution would be attempting to pre-fill the buffer using
getdents, which would fail with EBADF for us, but that seems more
complex and error-prone and involves either code duplication or
refactoring, so the simple fix with an additional inexpensive syscall
is what I've made for now.
This commit is contained in:
Rich Felker 2019-02-07 12:51:02 -05:00
parent 1dd915c370
commit 042b3ee452
1 changed files with 4 additions and 0 deletions
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4
src/dirent/fdopendir.c
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@ -13,6 +13,10 @@ DIR *fdopendir(int fd)
if (fstat(fd, &st) < 0) {
return 0;
}
if (fcntl(fd, F_GETFL) & O_PATH) {
errno = EBADF;
return 0;
}
if (!S_ISDIR(st.st_mode)) {
errno = ENOTDIR;
return 0;