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authorJan Kara <jack@suse.cz>2012-06-12 18:20:37 +0400
committerAl Viro <viro@zeniv.linux.org.uk>2012-07-31 09:45:47 +0400
commit14da9200140f8d722ad1767dfabadebd8b34f2ad (patch)
treeea5d88b091999f7a64af0b9d335d7cad4c79edfb /fs/open.c
parent5d37e9e6dec65cd21be68ee92de99686213e916b (diff)
downloadlinux-14da9200140f8d722ad1767dfabadebd8b34f2ad.tar.xz
fs: Protect write paths by sb_start_write - sb_end_write
There are several entry points which dirty pages in a filesystem. mmap (handled by block_page_mkwrite()), buffered write (handled by __generic_file_aio_write()), splice write (generic_file_splice_write), truncate, and fallocate (these can dirty last partial page - handled inside each filesystem separately). Protect these places with sb_start_write() and sb_end_write(). ->page_mkwrite() calls are particularly complex since they are called with mmap_sem held and thus we cannot use standard sb_start_write() due to lock ordering constraints. We solve the problem by using a special freeze protection sb_start_pagefault() which ranks below mmap_sem. BugLink: https://bugs.launchpad.net/bugs/897421 Tested-by: Kamal Mostafa <kamal@canonical.com> Tested-by: Peter M. Petrakis <peter.petrakis@canonical.com> Tested-by: Dann Frazier <dann.frazier@canonical.com> Tested-by: Massimo Morana <massimo.morana@canonical.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/open.c')
-rw-r--r--fs/open.c7
1 files changed, 6 insertions, 1 deletions
diff --git a/fs/open.c b/fs/open.c
index 9ddc18565503..f3d96e7e7b19 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -164,11 +164,13 @@ static long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
if (IS_APPEND(inode))
goto out_putf;
+ sb_start_write(inode->i_sb);
error = locks_verify_truncate(inode, file, length);
if (!error)
error = security_path_truncate(&file->f_path);
if (!error)
error = do_truncate(dentry, length, ATTR_MTIME|ATTR_CTIME, file);
+ sb_end_write(inode->i_sb);
out_putf:
fput(file);
out:
@@ -266,7 +268,10 @@ int do_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
if (!file->f_op->fallocate)
return -EOPNOTSUPP;
- return file->f_op->fallocate(file, mode, offset, len);
+ sb_start_write(inode->i_sb);
+ ret = file->f_op->fallocate(file, mode, offset, len);
+ sb_end_write(inode->i_sb);
+ return ret;
}
SYSCALL_DEFINE(fallocate)(int fd, int mode, loff_t offset, loff_t len)