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a620bd7935
The kernel interface uses type unsigned int, but there is an internal conversion to int, so INT_MAX is the correct limit. Part of the buffer will always be unused, but this is not a problem. Such huge buffers do not occur in practice anyway. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
133 lines
4.4 KiB
C
133 lines
4.4 KiB
C
/* Get directory entries. Linux LFS version.
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Copyright (C) 1997-2019 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library. If not, see
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<http://www.gnu.org/licenses/>. */
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#include <string.h>
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#include <dirent.h>
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#include <errno.h>
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#include <limits.h>
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/* The kernel struct linux_dirent64 matches the 'struct dirent64' type. */
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ssize_t
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__getdents64 (int fd, void *buf, size_t nbytes)
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{
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/* The system call takes an unsigned int argument, and some length
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checks in the kernel use an int type. */
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if (nbytes > INT_MAX)
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nbytes = INT_MAX;
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return INLINE_SYSCALL_CALL (getdents64, fd, buf, nbytes);
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}
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libc_hidden_def (__getdents64)
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weak_alias (__getdents64, getdents64)
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#if _DIRENT_MATCHES_DIRENT64
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strong_alias (__getdents64, __getdents)
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#else
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# include <shlib-compat.h>
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# if SHLIB_COMPAT(libc, GLIBC_2_1, GLIBC_2_2)
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# include <olddirent.h>
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# include <unistd.h>
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static ssize_t
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handle_overflow (int fd, __off64_t offset, ssize_t count)
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{
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/* If this is the first entry in the buffer, we can report the
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error. */
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if (offset == 0)
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{
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__set_errno (EOVERFLOW);
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return -1;
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}
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/* Otherwise, seek to the overflowing entry, so that the next call
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will report the error, and return the data read so far. */
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if (__lseek64 (fd, offset, SEEK_SET) != 0)
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return -1;
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return count;
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}
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ssize_t
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__old_getdents64 (int fd, char *buf, size_t nbytes)
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{
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/* We do not move the individual directory entries. This is only
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possible if the target type (struct __old_dirent64) is smaller
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than the source type. */
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_Static_assert (offsetof (struct __old_dirent64, d_name)
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<= offsetof (struct dirent64, d_name),
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"__old_dirent64 is larger than dirent64");
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_Static_assert (__alignof__ (struct __old_dirent64)
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<= __alignof__ (struct dirent64),
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"alignment of __old_dirent64 is larger than dirent64");
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ssize_t retval = INLINE_SYSCALL_CALL (getdents64, fd, buf, nbytes);
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if (retval > 0)
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{
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/* This is the marker for the first entry. Offset 0 is reserved
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for the first entry (see rewinddir). Here, we use it as a
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marker for the first entry in the buffer. We never actually
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seek to offset 0 because handle_overflow reports the error
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directly, so it does not matter that the offset is incorrect
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if entries have been read from the descriptor before (so that
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the descriptor is not actually at offset 0). */
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__off64_t previous_offset = 0;
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char *p = buf;
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char *end = buf + retval;
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while (p < end)
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{
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struct dirent64 *source = (struct dirent64 *) p;
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/* Copy out the fixed-size data. */
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__ino_t ino = source->d_ino;
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__off64_t offset = source->d_off;
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unsigned int reclen = source->d_reclen;
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unsigned char type = source->d_type;
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/* Check for ino_t overflow. */
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if (__glibc_unlikely (ino != source->d_ino))
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return handle_overflow (fd, previous_offset, p - buf);
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/* Convert to the target layout. Use a separate struct and
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memcpy to side-step aliasing issues. */
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struct __old_dirent64 result;
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result.d_ino = ino;
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result.d_off = offset;
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result.d_reclen = reclen;
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result.d_type = type;
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/* Write the fixed-sized part of the result to the
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buffer. */
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size_t result_name_offset = offsetof (struct __old_dirent64, d_name);
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memcpy (p, &result, result_name_offset);
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/* Adjust the position of the name if necessary. Copy
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everything until the end of the record, including the
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terminating NUL byte. */
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if (result_name_offset != offsetof (struct dirent64, d_name))
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memmove (p + result_name_offset, source->d_name,
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reclen - offsetof (struct dirent64, d_name));
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p += reclen;
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previous_offset = offset;
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}
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}
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return retval;
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}
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# endif /* SHLIB_COMPAT(libc, GLIBC_2_1, GLIBC_2_2) */
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#endif /* _DIRENT_MATCHES_DIRENT64 */
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