[Ocfs2-devel] [PATCH 06/15] vfs: strengthen checking of file range inputs to clone/dedupe range

[Darrick J. Wong]

From: Darrick J. Wong <darrick.wong at oracle.com>

Clone range is an optimization on a regular file write.  File writes
that extend the file length are subject to various constraints which are
not checked by clonerange.  This is a correctness problem, because we're
never allowed to touch ranges that the page cache can't support
(s_maxbytes); we're not supposed to deal with large offsets
(MAX_NON_LFS) if O_LARGEFILE isn't set; and we must obey resource limits
(RLIMIT_FSIZE).

Therefore, add these checks to the new generic_clone_checks function so
that we curtail unexpected behavior.

Signed-off-by: Darrick J. Wong <darrick.wong at oracle.com>
---
 mm/filemap.c |   31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)


diff --git a/mm/filemap.c b/mm/filemap.c
index 68ec91d05c7b..f74391721234 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -3015,6 +3015,37 @@ int generic_clone_checks(struct file *file_in, loff_t pos_in,
 		return -EINVAL;
 	count = min(count, size_in - (uint64_t)pos_in);
 
+	/* Don't exceed RLMIT_FSIZE in the file we're writing into. */
+	if (limit != RLIM_INFINITY) {
+		if (pos_out >= limit) {
+			send_sig(SIGXFSZ, current, 0);
+			return -EFBIG;
+		}
+		count = min(count, limit - (uint64_t)pos_out);
+	}
+
+	/* Don't exceed the LFS limits. */
+	if (unlikely(pos_out + count > MAX_NON_LFS &&
+				!(file_out->f_flags & O_LARGEFILE))) {
+		if (pos_out >= MAX_NON_LFS)
+			return -EFBIG;
+		count = min(count, MAX_NON_LFS - (uint64_t)pos_out);
+	}
+	if (unlikely(pos_in + count > MAX_NON_LFS &&
+				!(file_in->f_flags & O_LARGEFILE))) {
+		if (pos_in >= MAX_NON_LFS)
+			return -EFBIG;
+		count = min(count, MAX_NON_LFS - (uint64_t)pos_in);
+	}
+
+	/* Don't operate on ranges the page cache doesn't support. */
+	if (unlikely(pos_out >= inode_out->i_sb->s_maxbytes ||
+		     pos_in >= inode_in->i_sb->s_maxbytes))
+		return -EFBIG;
+
+	count = min(count, inode_out->i_sb->s_maxbytes - (uint64_t)pos_out);
+	count = min(count, inode_in->i_sb->s_maxbytes - (uint64_t)pos_in);
+
 	/*
 	 * If the user wanted us to link to the infile's EOF, round up to the
 	 * next block boundary for this check.