erofs: restrict pcluster size limitations

Error out if {en,de}encoded size of a pcluster is unsupported:
  Maximum supported encoded size (of a pcluster):  1 MiB
  Maximum supported decoded size (of a pcluster): 12 MiB

Users can still choose to use supported large configurations (e.g.,
for archival purposes), but there may be performance penalties in
low-memory scenarios compared to smaller pclusters.

Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20240912074156.2925394-1-hsiangkao@linux.alibaba.com

diff --git a/fs/erofs/erofs_fs.h b/fs/erofs/erofs_fs.h
index 6c0c270c42e1546c62b096854ffe91f59c13cf3e..c8f2ae845bd29e84a5bf2739f49971370f8db15a 100644 (file)
--- a/fs/erofs/erofs_fs.h
+++ b/fs/erofs/erofs_fs.h
@@ -288,9 +288,12 @@ struct erofs_dirent {
 
 #define EROFS_NAME_LEN      255
 
-/* maximum supported size of a physical compression cluster */
+/* maximum supported encoded size of a physical compressed cluster */
 #define Z_EROFS_PCLUSTER_MAX_SIZE      (1024 * 1024)
 
+/* maximum supported decoded size of a physical compressed cluster */
+#define Z_EROFS_PCLUSTER_MAX_DSIZE     (12 * 1024 * 1024)
+
 /* available compression algorithm types (for h_algorithmtype) */
 enum {
        Z_EROFS_COMPRESSION_LZ4         = 0,

diff --git a/fs/erofs/zmap.c b/fs/erofs/zmap.c
index 403af6e31d5b2c798ae1736057c3f4d5158645c0..e980e29873a56e4b5d70e3873d04adc958b54259 100644 (file)
--- a/fs/erofs/zmap.c
+++ b/fs/erofs/zmap.c
@@ -687,32 +687,30 @@ int z_erofs_map_blocks_iter(struct inode *inode, struct erofs_map_blocks *map,
        int err = 0;
 
        trace_erofs_map_blocks_enter(inode, map, flags);
-
-       /* when trying to read beyond EOF, leave it unmapped */
-       if (map->m_la >= inode->i_size) {
+       if (map->m_la >= inode->i_size) {       /* post-EOF unmapped extent */
                map->m_llen = map->m_la + 1 - inode->i_size;
                map->m_la = inode->i_size;
                map->m_flags = 0;
-               goto out;
-       }
-
-       err = z_erofs_fill_inode_lazy(inode);
-       if (err)
-               goto out;
-
-       if ((vi->z_advise & Z_EROFS_ADVISE_FRAGMENT_PCLUSTER) &&
-           !vi->z_tailextent_headlcn) {
-               map->m_la = 0;
-               map->m_llen = inode->i_size;
-               map->m_flags = EROFS_MAP_MAPPED | EROFS_MAP_FULL_MAPPED |
-                               EROFS_MAP_FRAGMENT;
-               goto out;
+       } else {
+               err = z_erofs_fill_inode_lazy(inode);
+               if (!err) {
+                       if ((vi->z_advise & Z_EROFS_ADVISE_FRAGMENT_PCLUSTER) &&
+                           !vi->z_tailextent_headlcn) {
+                               map->m_la = 0;
+                               map->m_llen = inode->i_size;
+                               map->m_flags = EROFS_MAP_MAPPED |
+                                       EROFS_MAP_FULL_MAPPED | EROFS_MAP_FRAGMENT;
+                       } else {
+                               err = z_erofs_do_map_blocks(inode, map, flags);
+                       }
+               }
+               if (!err && (map->m_flags & EROFS_MAP_ENCODED) &&
+                   unlikely(map->m_plen > Z_EROFS_PCLUSTER_MAX_SIZE ||
+                            map->m_llen > Z_EROFS_PCLUSTER_MAX_DSIZE))
+                       err = -EOPNOTSUPP;
+               if (err)
+                       map->m_llen = 0;
        }
-
-       err = z_erofs_do_map_blocks(inode, map, flags);
-out:
-       if (err)
-               map->m_llen = 0;
        trace_erofs_map_blocks_exit(inode, map, flags, err);
        return err;
 }