[Regression] Editting stale symlink removes symlink and creates file symlink points to

[Andrew V. Samoilov]

Pavel Roskin wrote:
> Hello!
> 
> 
>>Max Derzhak <max /at/linux.zp.ua> reported new regression in mcedit.  If 
>>you type F4 on stale symlink and press Esc-Esc or F10 after it (no 
>>editting at all) mcedit creates empty file symlink points to and removes 
>>original symlink.
> 
> 
> The problem is not related to VFS, so I'll talk in terms on libc
> functions.
> 
> stat() fails, the file is opened with O_CREAT, creating the link target.  
> If the file has not been modified, it's removed.  open() resolves
> symlinks, unlink() doesn't, hence the result.
> 
> I think that editing stale symlinks is insane.  If stat() fails, then we
> expect to create a new file.  That's what O_EXCL is for.  I'm applying a
> patch that uses O_EXCL whenever stat() fails.  Editing stale symlinks is
> now impossible.  I think it's reasonable.
> 
> I realize that O_EXCL may not be implemented in every VFS, but it's a
> separate problem.  Actually, direntry.c knows this flag, so only
> filesystems with its own open() need to be changed.
> 

Fine and elegant solution!

Thanks a lot!

-- 
Regards,
Andrew V. Samoilov