copy_file_range (which calls generic_copy_file_checks) uses the inode file size to adjust the copy count parameter. This breaks with special filesystems like procfs/sysfs/debugfs/tracefs, where the file size appears to be zero, but content is actually returned when a read operation is performed. Other issues would also happen on partial writes, as the function would attempt to seek in the input file.
Use the newly introduced FS_GENERATED_CONTENT filesystem flag to return -EOPNOTSUPP: applications can then retry with a more usual read/write based file copy (the fallback code is usually already present to handle older kernels). Signed-off-by: Nicolas Boichat <[email protected]> --- fs/read_write.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/fs/read_write.c b/fs/read_write.c index 0029ff2b0ca8..80322e89fb0a 100644 --- a/fs/read_write.c +++ b/fs/read_write.c @@ -1485,6 +1485,9 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in, if (flags != 0) return -EINVAL; + if (file_inode(file_in)->i_sb->s_type->fs_flags & FS_GENERATED_CONTENT) + return -EOPNOTSUPP; + ret = generic_copy_file_checks(file_in, pos_in, file_out, pos_out, &len, flags); if (unlikely(ret)) -- 2.30.0.478.g8a0d178c01-goog
