From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
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@xxxxxxxxxx>
---
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.
