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author | Jan Kara <jack@suse.cz> | 2014-02-18 12:00:21 +0100 |
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committer | Jan Kara <jack@suse.cz> | 2014-02-20 21:56:00 +0100 |
commit | 09ebb17ab476b6ac1cc07b53d07e88f4d31ee4d3 (patch) | |
tree | 609dcf7d4bb825ea1978913c29bff3687a1247ac /lib/zlib_deflate/Makefile | |
parent | 45a22f4c11fef4ecd5c61c0a299cd3f23d77be8e (diff) | |
download | op-kernel-dev-09ebb17ab476b6ac1cc07b53d07e88f4d31ee4d3.zip op-kernel-dev-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 'lib/zlib_deflate/Makefile')
0 files changed, 0 insertions, 0 deletions