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ext4: Improve feature checking

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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>
This commit is contained in:
Richard Weinberger 2024-07-29 23:37:31 +02:00 • committed by Tom Rini
parent 37dc8c2e98
commit faf73fb70d
3 changed files with 76 additions and 3 deletions
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14
fs/ext4/ext4_common.c
View file

@ -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),

12
fs/ext4/ext4_write.c
View file

@ -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;
}

53
include/ext4fs.h
View file

@ -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