On 03/01/09 22:03, Adam Osuchowski wrote:
> There is a race condition in vim 7.2 (and probably in earlier too) on POSIX
> platforms. Below, there is fragment of strace output related to this problem.
>
>
> stat64("testfile~", 0xbfc35dbc) = -1 ENOENT (No such file or
> directory)
> stat64("testfile", {st_mode=S_IFREG|0600, st_size=12, ...}) = 0
> unlink("testfile~") = -1 ENOENT (No such file or
> directory)
> rename("testfile", "testfile~") = 0
> open("testfile", O_WRONLY|O_CREAT|O_TRUNC, 0600) = 3
> write(3, "test test test\n"..., 15) = 15
> fsync(3) = 0
> stat64("testfile", {st_mode=S_IFREG|0600, st_size=15, ...}) = 0
> stat64("testfile", {st_mode=S_IFREG|0600, st_size=15, ...}) = 0
> close(3) = 0
>
>
> Problematic situation take place during file saving between rename and open,
> open and write as well as write and close syscalls. There are points at
> which another process attempting to access file may run into trouble.
> There is, for example, possibility to:
>
> - if application, which expects existence of file, would try to open it
> between vim rename and open syscalls, it will fail due to lack of this
> file,
>
> - if other process creates file with the same name between vim rename and
> open syscalls, it will be overriden by vim (it works with symlinks too,
> so it can be used by attacker to damage other files),
>
> - if application will read file while vim will write to it, the contents
> may be badly read due to temporarily partially record.
>
> Vim rather should create new, its own, temporary file with unique name,
> write content, close it and then, atomically rename it to original name.
>
> Regards.
See
:help backup
:help 'backup'
:help 'writebackup'
:help 'backupcopy'
:help timestamp
Best regards,
Tony.
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