09ebb17ab4
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>
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| .. | ||
| Kconfig | ||
| Makefile | ||
| balloc.c | ||
| dir.c | ||
| directory.c | ||
| ecma_167.h | ||
| file.c | ||
| ialloc.c | ||
| inode.c | ||
| lowlevel.c | ||
| misc.c | ||
| namei.c | ||
| osta_udf.h | ||
| partition.c | ||
| super.c | ||
| symlink.c | ||
| truncate.c | ||
| udf_i.h | ||
| udf_sb.h | ||
| udfdecl.h | ||
| udfend.h | ||
| udftime.c | ||
| unicode.c | ||