Evaluate the filesystem incompat and ro_compat bit fields to judge whether the filesystem can be read or written. For the read side only a scary warning is shown so far. I'd love to abort mounting too, but I fear this will break some setups where the driver works by chance.
Signed-off-by: Richard Weinberger richard@nod.at --- Changes since v2: - Add EXT4_FEATURE_RO_COMPAT_GDT_CSUM to EXT4_FEATURE_RO_COMPAT_SUPP set --- fs/ext4/ext4_common.c | 14 ++++++++++++ fs/ext4/ext4_write.c | 12 ++++++++-- include/ext4fs.h | 53 ++++++++++++++++++++++++++++++++++++++++++- 3 files changed, 76 insertions(+), 3 deletions(-)
diff --git a/fs/ext4/ext4_common.c b/fs/ext4/ext4_common.c index 52152a2295..7cf0160c40 100644 --- a/fs/ext4/ext4_common.c +++ b/fs/ext4/ext4_common.c @@ -2383,6 +2383,20 @@ int ext4fs_mount(void) fs->inodesz = 128; fs->gdsize = 32; } else { + int missing = __le32_to_cpu(data->sblock.feature_incompat) & + ~(EXT4_FEATURE_INCOMPAT_SUPP | + EXT4_FEATURE_INCOMPAT_SUPP_LAZY_RO); + + if (missing) { + /* + * This code used to be relaxed about feature flags. + * We don't stop the mount to avoid breaking existing setups. + * But, incompatible features can cause serious read errors. + */ + log_err("fs uses incompatible features: %08x, ignoring\n", + missing); + } + debug("EXT4 features COMPAT: %08x INCOMPAT: %08x RO_COMPAT: %08x\n", __le32_to_cpu(data->sblock.feature_compatibility), __le32_to_cpu(data->sblock.feature_incompat), diff --git a/fs/ext4/ext4_write.c b/fs/ext4/ext4_write.c index a2dfff8197..d109ed6e90 100644 --- a/fs/ext4/ext4_write.c +++ b/fs/ext4/ext4_write.c @@ -866,6 +866,7 @@ int ext4fs_write(const char *fname, const char *buffer, ALLOC_CACHE_ALIGN_BUFFER(char, filename, 256); bool store_link_in_inode = false; memset(filename, 0x00, 256); + int missing_feat;
if (type != FILETYPE_REG && type != FILETYPE_SYMLINK) return -1; @@ -879,8 +880,15 @@ int ext4fs_write(const char *fname, const char *buffer, return -1; }
- if (le32_to_cpu(fs->sb->feature_ro_compat) & EXT4_FEATURE_RO_COMPAT_METADATA_CSUM) { - printf("Unsupported feature metadata_csum found, not writing.\n"); + missing_feat = le32_to_cpu(fs->sb->feature_incompat) & ~EXT4_FEATURE_INCOMPAT_SUPP; + if (missing_feat) { + log_err("Unsupported features found %08x, not writing.\n", missing_feat); + return -1; + } + + missing_feat = le32_to_cpu(fs->sb->feature_ro_compat) & ~EXT4_FEATURE_RO_COMPAT_SUPP; + if (missing_feat) { + log_err("Unsupported RO compat features found %08x, not writing.\n", missing_feat); return -1; }
diff --git a/include/ext4fs.h b/include/ext4fs.h index d96edfd057..41f9eb8bd3 100644 --- a/include/ext4fs.h +++ b/include/ext4fs.h @@ -34,12 +34,63 @@ struct disk_partition; #define EXT4_TOPDIR_FL 0x00020000 /* Top of directory hierarchies*/ #define EXT4_EXTENTS_FL 0x00080000 /* Inode uses extents */ #define EXT4_EXT_MAGIC 0xf30a -#define EXT4_FEATURE_RO_COMPAT_GDT_CSUM 0x0010 + +#define EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER 0x0001 +#define EXT4_FEATURE_RO_COMPAT_LARGE_FILE 0x0002 +#define EXT4_FEATURE_RO_COMPAT_BTREE_DIR 0x0004 +#define EXT4_FEATURE_RO_COMPAT_HUGE_FILE 0x0008 +#define EXT4_FEATURE_RO_COMPAT_GDT_CSUM 0x0010 +#define EXT4_FEATURE_RO_COMPAT_DIR_NLINK 0x0020 +#define EXT4_FEATURE_RO_COMPAT_EXTRA_ISIZE 0x0040 +#define EXT4_FEATURE_RO_COMPAT_QUOTA 0x0100 +#define EXT4_FEATURE_RO_COMPAT_BIGALLOC 0x0200 #define EXT4_FEATURE_RO_COMPAT_METADATA_CSUM 0x0400 + +#define EXT4_FEATURE_INCOMPAT_FILETYPE 0x0002 +#define EXT4_FEATURE_INCOMPAT_RECOVER 0x0004 #define EXT4_FEATURE_INCOMPAT_EXTENTS 0x0040 #define EXT4_FEATURE_INCOMPAT_64BIT 0x0080 +#define EXT4_FEATURE_INCOMPAT_MMP 0x0100 +#define EXT4_FEATURE_INCOMPAT_FLEX_BG 0x0200 +#define EXT4_FEATURE_INCOMPAT_CSUM_SEED 0x2000 +#define EXT4_FEATURE_INCOMPAT_ENCRYPT 0x10000 + #define EXT4_INDIRECT_BLOCKS 12
+/* + * Incompat features supported by this implementation. + */ +#define EXT4_FEATURE_INCOMPAT_SUPP (EXT4_FEATURE_INCOMPAT_FILETYPE | \ + EXT4_FEATURE_INCOMPAT_RECOVER | \ + EXT4_FEATURE_INCOMPAT_EXTENTS | \ + EXT4_FEATURE_INCOMPAT_64BIT | \ + EXT4_FEATURE_INCOMPAT_FLEX_BG) + +/* + * Incompat features supported by this implementation only in a lazy + * way, good enough for reading files. + * + * - Multi mount protection (mmp) is not supported, but for read-only + * we get away with it. + * - Same for metadata_csum_seed and metadata_csum. + * - The implementation has also no clue about fscrypt, but it can read + * unencrypted files. Reading encrypted files will read garbage. + */ +#define EXT4_FEATURE_INCOMPAT_SUPP_LAZY_RO (EXT4_FEATURE_INCOMPAT_MMP | \ + EXT4_FEATURE_INCOMPAT_CSUM_SEED | \ + EXT4_FEATURE_INCOMPAT_ENCRYPT) + +/* + * Read-only compat features we support. + * If unknown ro compat features are detected, writing to the fs is denied. + */ +#define EXT4_FEATURE_RO_COMPAT_SUPP (EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER | \ + EXT4_FEATURE_RO_COMPAT_LARGE_FILE | \ + EXT4_FEATURE_RO_COMPAT_HUGE_FILE | \ + EXT4_FEATURE_RO_COMPAT_GDT_CSUM | \ + EXT4_FEATURE_RO_COMPAT_DIR_NLINK | \ + EXT4_FEATURE_RO_COMPAT_EXTRA_ISIZE) + #define EXT4_BG_INODE_UNINIT 0x0001 #define EXT4_BG_BLOCK_UNINIT 0x0002 #define EXT4_BG_INODE_ZEROED 0x0004