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Check for immutable/append flag in fallocate path

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In the fallocate path the kernel doesn't check for the immutable/append
flag. It's possible to have a race condition in this scenario: an
application open a file in read/write and it does something, meanwhile
root set the immutable flag on the file, the application at that point
can call fallocate with success. In addition, we don't allow to do any
unreserve operation on an append only file but only the reserve one.

Signed-off-by: Marco Stornelli <marco.stornelli@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Marco Stornelli 2011-03-05 11:10:19 +01:00 committed by Al Viro
parent 991ac30d8b
commit 1ca551c6ca
1 changed files with 8 additions and 0 deletions
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8
fs/open.c
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@ -233,6 +233,14 @@ int do_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
if (!(file->f_mode & FMODE_WRITE))
return -EBADF;
/* It's not possible punch hole on append only file */
if (mode & FALLOC_FL_PUNCH_HOLE && IS_APPEND(inode))
return -EPERM;
if (IS_IMMUTABLE(inode))
return -EPERM;
/*
* Revalidate the write permissions, in case security policy has
* changed since the files were opened.