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Fixed positive seek bounds checking

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This bug was a result of an annoying corner case around intermingling
signed and unsigned offsets. The boundary check that prevents seeking
a file to a position before the file was preventing valid seeks with
positive offsets.

This corner case is a bit more complicated than it looks because the
offset is signed, while the size of the file is unsigned. Simply
casting both to signed or unsigned offsets won't handle large files.
This commit is contained in:
Christopher Haster 2018-01-03 15:00:04 -06:00
parent be22d3449f
commit aea3d3db46
2 changed files with 18 additions and 2 deletions
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4
lfs.c
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@ -1635,13 +1635,13 @@ lfs_soff_t lfs_file_seek(lfs_t *lfs, lfs_file_t *file,
if (whence == LFS_SEEK_SET) {
file->pos = off;
} else if (whence == LFS_SEEK_CUR) {
if ((lfs_off_t)-off > file->pos) {
if (off < 0 && (lfs_off_t)-off > file->pos) {
return LFS_ERR_INVAL;
}
file->pos = file->pos + off;
} else if (whence == LFS_SEEK_END) {
if ((lfs_off_t)-off > file->size) {
if (off < 0 && (lfs_off_t)-off > file->size) {
return LFS_ERR_INVAL;
}

16
tests/test_seek.sh
View File

@ -133,6 +133,14 @@ tests/test.py << TEST
lfs_file_read(&lfs, &file[0], buffer, size) => size;
memcmp(buffer, "kittycatcat", size) => 0;
lfs_file_seek(&lfs, &file[0], 0, LFS_SEEK_CUR) => size;
lfs_file_read(&lfs, &file[0], buffer, size) => size;
memcmp(buffer, "kittycatcat", size) => 0;
lfs_file_seek(&lfs, &file[0], size, LFS_SEEK_CUR) => 3*size;
lfs_file_read(&lfs, &file[0], buffer, size) => size;
memcmp(buffer, "kittycatcat", size) => 0;
lfs_file_seek(&lfs, &file[0], pos, LFS_SEEK_SET) => pos;
lfs_file_read(&lfs, &file[0], buffer, size) => size;
memcmp(buffer, "kittycatcat", size) => 0;
@ -174,6 +182,14 @@ tests/test.py << TEST
lfs_file_read(&lfs, &file[0], buffer, size) => size;
memcmp(buffer, "kittycatcat", size) => 0;
lfs_file_seek(&lfs, &file[0], 0, LFS_SEEK_CUR) => size;
lfs_file_read(&lfs, &file[0], buffer, size) => size;
memcmp(buffer, "kittycatcat", size) => 0;
lfs_file_seek(&lfs, &file[0], size, LFS_SEEK_CUR) => 3*size;
lfs_file_read(&lfs, &file[0], buffer, size) => size;
memcmp(buffer, "kittycatcat", size) => 0;
lfs_file_seek(&lfs, &file[0], pos, LFS_SEEK_SET) => pos;
lfs_file_read(&lfs, &file[0], buffer, size) => size;
memcmp(buffer, "kittycatcat", size) => 0;