diff options
Diffstat (limited to 'sysdeps/unix/sysv/linux/getdents.c')
| -rw-r--r-- | sysdeps/unix/sysv/linux/getdents.c | 45 |
1 files changed, 26 insertions, 19 deletions
diff --git a/sysdeps/unix/sysv/linux/getdents.c b/sysdeps/unix/sysv/linux/getdents.c index 40b31617ef..b4b12d48eb 100644 --- a/sysdeps/unix/sysv/linux/getdents.c +++ b/sysdeps/unix/sysv/linux/getdents.c @@ -49,11 +49,11 @@ struct kernel_dirent /* The problem here is that we cannot simply read the next NBYTES bytes. We need to take the additional field into account. We use - some heuristic. Assume the directory contains names with at least - 3 characters we can compute a maximum number of entries which fit - in the buffer. Taking this number allows us to specify a correct - number of bytes to read. If we should be wrong, we can reset the - file descriptor. */ + some heuristic. Assuming the directory contains names with 14 + characters on average we can compute an estimate number of entries + which fit in the buffer. Taking this number allows us to specify a + correct number of bytes to read. If we should be wrong, we can reset + the file descriptor. */ ssize_t __getdirentries (fd, buf, nbytes, basep) int fd; @@ -62,12 +62,16 @@ __getdirentries (fd, buf, nbytes, basep) off_t *basep; { off_t base = __lseek (fd, (off_t) 0, SEEK_CUR); + off_t last_offset = base; size_t red_nbytes; struct kernel_dirent *skdp, *kdp; struct dirent *dp; int retval; + const size_t size_diff = (offsetof (struct dirent, d_name) + - offsetof (struct kernel_dirent, d_name)); - red_nbytes = nbytes - (nbytes / (offsetof (struct dirent, d_name) + 3)); + red_nbytes = nbytes - ((nbytes / (offsetof (struct dirent, d_name) + 14)) + * size_diff); dp = (struct dirent *) buf; skdp = kdp = __alloca (red_nbytes); @@ -76,26 +80,29 @@ __getdirentries (fd, buf, nbytes, basep) while ((char *) kdp < (char *) skdp + retval) { - const size_t size_diff = MAX (offsetof (struct dirent, d_name) - - offsetof (struct kernel_dirent, d_name), - __alignof__ (struct dirent)); + const size_t alignment = __alignof__ (struct dirent); + /* Since kdp->d_reclen is already aligned for the kernel structure + this may compute a value that is bigger than necessary. */ + size_t new_reclen = ((kdp->d_reclen + size_diff + alignment - 1) + & ~(alignment - 1)); + if ((char *) dp + new_reclen > buf + nbytes) + { + /* Our heuristic failed. We read too many entries. Reset + the stream. */ + __lseek (fd, last_offset, SEEK_SET); + break; + } + + last_offset = kdp->d_off; dp->d_ino = kdp->d_ino; dp->d_off = kdp->d_off; - dp->d_reclen = kdp->d_reclen + size_diff; + dp->d_reclen = new_reclen; dp->d_type = DT_UNKNOWN; memcpy (dp->d_name, kdp->d_name, kdp->d_reclen - offsetof (struct kernel_dirent, d_name)); - dp = (struct dirent *) (((char *) dp) + dp->d_reclen); + dp = (struct dirent *) ((char *) dp + new_reclen); kdp = (struct kernel_dirent *) (((char *) kdp) + kdp->d_reclen); - - if ((char *) dp >= buf + nbytes) - { - /* Our heuristic failed. We read too many entries. Reset - the stream. */ - off_t used = ((char *) kdp - (char *) buf) - (nbytes - red_nbytes); - base = __lseek (fd, retval - used, SEEK_CUR); - } } if (basep) |