fs/ntfs3: resize log->one_page_buf when adopting on-disk page size

log_replay() allocates log->one_page_buf using the page size that was
chosen from the host PAGE_SIZE:

	log->one_page_buf = kmalloc(log->page_size, GFP_NOFS);

Later, when a restart area is found, the log page size recorded on disk
is adopted:

	t32 = le32_to_cpu(log->rst_info.r_page->sys_page_size);
	if (log->page_size != t32) {
		log->l_size = log->orig_file_size;
		log->page_size = norm_file_page(t32, &log->l_size,
						t32 == DefaultLogPageSize);
	}

If the on-disk page size is larger than the size used for the initial
allocation, log->page_size grows but one_page_buf is left at its
original, smaller size. A subsequent unaligned read_log_page() then
reads log->page_size bytes into the undersized scratch buffer:

	page_buf = page_off ? log->one_page_buf : *buffer;
	err = ntfs_read_run_nb_ra(ni->mi.sbi, &ni->file.run, page_vbo, page_buf,
				  log->page_size, NULL, &log->read_ahead);

overflowing the allocation. This is reachable when mounting a dirty
NTFS volume whose log was formatted with a page size larger than the
buffer initially allocated on the mounting host (for example a 64K-log
volume mounted on a host that allocated a 4K scratch buffer).

Grow one_page_buf when the adopted on-disk page size exceeds the size
used for the initial allocation. On krealloc() failure the original
buffer is left intact and freed by the existing error path.

Fixes: b46acd6a6a627 ("fs/ntfs3: Add NTFS journal")
Reported-by: Carol L Soto <csoto@nvidia.com>
Signed-off-by: Jamie Nguyen <jamien@nvidia.com>
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>

diff --git a/fs/ntfs3/fslog.c b/fs/ntfs3/fslog.c
index e5ff99a2e6a2aec320810c837bdaea298160f05e..f038c799e7ac494c17522b337148e9d31969674c 100644 (file)
--- a/fs/ntfs3/fslog.c
+++ b/fs/ntfs3/fslog.c
@@ -4005,9 +4005,28 @@ check_restart_area:
         */
        t32 = le32_to_cpu(log->rst_info.r_page->sys_page_size);
        if (log->page_size != t32) {
+               u32 old_page_size = log->page_size;
+
                log->l_size = log->orig_file_size;
                log->page_size = norm_file_page(t32, &log->l_size,
                                                t32 == DefaultLogPageSize);
+
+               /*
+                * If the adopted on-disk page size is larger than the size used
+                * to allocate one_page_buf above, grow the scratch buffer so a
+                * later read_log_page() cannot overflow it.
+                */
+               if (log->page_size > old_page_size) {
+                       void *buf;
+
+                       buf = krealloc(log->one_page_buf, log->page_size,
+                                      GFP_NOFS);
+                       if (!buf) {
+                               err = -ENOMEM;
+                               goto out;
+                       }
+                       log->one_page_buf = buf;
+               }
        }
 
        if (log->page_size != t32 ||