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Subject[PATCH AUTOSEL 4.18 43/45] udf: Prevent write-unsupported filesystem to be remounted read-write
Date
From: Jan Kara <jack@suse.cz>

[ Upstream commit a9ad01bc759df79b0012f43ee52164391e31cd96 ]

There are certain filesystem features which we support for reading but
not for writing. We properly refuse to mount such filesystems read-write
however for some features (such as read-only partitions), we don't check
for these features when remounting the filesystem from read-only to
read-write. Thus such filesystems could be remounted read-write leading
to strange behavior (most likely crashes).

Fix the problem by marking in superblock whether the filesystem has some
features that are supported in read-only mode and check this flag during
remount.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/udf/super.c | 30 ++++++++++++++++--------------
fs/udf/udf_sb.h | 2 ++
2 files changed, 18 insertions(+), 14 deletions(-)

diff --git a/fs/udf/super.c b/fs/udf/super.c
index 74b13347cd94..e557d1317d0e 100644
--- a/fs/udf/super.c
+++ b/fs/udf/super.c
@@ -613,14 +613,11 @@ static int udf_remount_fs(struct super_block *sb, int *flags, char *options)
struct udf_options uopt;
struct udf_sb_info *sbi = UDF_SB(sb);
int error = 0;
- struct logicalVolIntegrityDescImpUse *lvidiu = udf_sb_lvidiu(sb);
+
+ if (!(*flags & SB_RDONLY) && UDF_QUERY_FLAG(sb, UDF_FLAG_RW_INCOMPAT))
+ return -EACCES;

sync_filesystem(sb);
- if (lvidiu) {
- int write_rev = le16_to_cpu(lvidiu->minUDFWriteRev);
- if (write_rev > UDF_MAX_WRITE_VERSION && !(*flags & SB_RDONLY))
- return -EACCES;
- }

uopt.flags = sbi->s_flags;
uopt.uid = sbi->s_uid;
@@ -1317,6 +1314,7 @@ static int udf_load_partdesc(struct super_block *sb, sector_t block)
ret = -EACCES;
goto out_bh;
}
+ UDF_SET_FLAG(sb, UDF_FLAG_RW_INCOMPAT);
ret = udf_load_vat(sb, i, type1_idx);
if (ret < 0)
goto out_bh;
@@ -2215,10 +2213,12 @@ static int udf_fill_super(struct super_block *sb, void *options, int silent)
UDF_MAX_READ_VERSION);
ret = -EINVAL;
goto error_out;
- } else if (minUDFWriteRev > UDF_MAX_WRITE_VERSION &&
- !sb_rdonly(sb)) {
- ret = -EACCES;
- goto error_out;
+ } else if (minUDFWriteRev > UDF_MAX_WRITE_VERSION) {
+ if (!sb_rdonly(sb)) {
+ ret = -EACCES;
+ goto error_out;
+ }
+ UDF_SET_FLAG(sb, UDF_FLAG_RW_INCOMPAT);
}

sbi->s_udfrev = minUDFWriteRev;
@@ -2236,10 +2236,12 @@ static int udf_fill_super(struct super_block *sb, void *options, int silent)
}

if (sbi->s_partmaps[sbi->s_partition].s_partition_flags &
- UDF_PART_FLAG_READ_ONLY &&
- !sb_rdonly(sb)) {
- ret = -EACCES;
- goto error_out;
+ UDF_PART_FLAG_READ_ONLY) {
+ if (!sb_rdonly(sb)) {
+ ret = -EACCES;
+ goto error_out;
+ }
+ UDF_SET_FLAG(sb, UDF_FLAG_RW_INCOMPAT);
}

if (udf_find_fileset(sb, &fileset, &rootdir)) {
diff --git a/fs/udf/udf_sb.h b/fs/udf/udf_sb.h
index 9dd3e1b9619e..f8e0d200271d 100644
--- a/fs/udf/udf_sb.h
+++ b/fs/udf/udf_sb.h
@@ -30,6 +30,8 @@
#define UDF_FLAG_LASTBLOCK_SET 16
#define UDF_FLAG_BLOCKSIZE_SET 17
#define UDF_FLAG_INCONSISTENT 18
+#define UDF_FLAG_RW_INCOMPAT 19 /* Set when we find RW incompatible
+ * feature */

#define UDF_PART_FLAG_UNALLOC_BITMAP 0x0001
#define UDF_PART_FLAG_UNALLOC_TABLE 0x0002
--
2.17.1
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