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authorJan Kara <jack@suse.cz>2014-02-18 12:00:21 +0100
committerJan Kara <jack@suse.cz>2014-02-20 21:56:00 +0100
commit09ebb17ab476b6ac1cc07b53d07e88f4d31ee4d3 (patch)
tree609dcf7d4bb825ea1978913c29bff3687a1247ac /fs/udf/file.c
parent45a22f4c11fef4ecd5c61c0a299cd3f23d77be8e (diff)
downloadlinux-stericsson-09ebb17ab476b6ac1cc07b53d07e88f4d31ee4d3.tar.gz
udf: Fix data corruption on file type conversion
UDF has two types of files - files with data stored in inode (ICB in UDF terminology) and files with data stored in external data blocks. We convert file from in-inode format to external format in udf_file_aio_write() when we find out data won't fit into inode any longer. However the following race between two O_APPEND writes can happen: CPU1 CPU2 udf_file_aio_write() udf_file_aio_write() down_write(&iinfo->i_data_sem); checks that i_size + count1 fits within inode => no need to convert up_write(&iinfo->i_data_sem); down_write(&iinfo->i_data_sem); checks that i_size + count2 fits within inode => no need to convert up_write(&iinfo->i_data_sem); generic_file_aio_write() - extends file by count1 bytes generic_file_aio_write() - extends file by count2 bytes Clearly if count1 + count2 doesn't fit into the inode, we overwrite kernel buffers beyond inode, possibly corrupting the filesystem as well. Fix the problem by acquiring i_mutex before checking whether write fits into the inode and using __generic_file_aio_write() afterwards which puts check and write into one critical section. Reported-by: Al Viro <viro@ZenIV.linux.org.uk> Signed-off-by: Jan Kara <jack@suse.cz>
Diffstat (limited to 'fs/udf/file.c')
-rw-r--r--fs/udf/file.c14
1 files changed, 12 insertions, 2 deletions
diff --git a/fs/udf/file.c b/fs/udf/file.c
index c02a27a19c6d..1037637957c7 100644
--- a/fs/udf/file.c
+++ b/fs/udf/file.c
@@ -144,6 +144,7 @@ static ssize_t udf_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
size_t count = iocb->ki_nbytes;
struct udf_inode_info *iinfo = UDF_I(inode);
+ mutex_lock(&inode->i_mutex);
down_write(&iinfo->i_data_sem);
if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) {
if (file->f_flags & O_APPEND)
@@ -156,6 +157,7 @@ static ssize_t udf_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
pos + count)) {
err = udf_expand_file_adinicb(inode);
if (err) {
+ mutex_unlock(&inode->i_mutex);
udf_debug("udf_expand_adinicb: err=%d\n", err);
return err;
}
@@ -169,9 +171,17 @@ static ssize_t udf_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
} else
up_write(&iinfo->i_data_sem);
- retval = generic_file_aio_write(iocb, iov, nr_segs, ppos);
- if (retval > 0)
+ retval = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos);
+ mutex_unlock(&inode->i_mutex);
+
+ if (retval > 0) {
+ ssize_t err;
+
mark_inode_dirty(inode);
+ err = generic_write_sync(file, iocb->ki_pos - retval, retval);
+ if (err < 0)
+ retval = err;
+ }
return retval;
}