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From: Alexey Sheplyakov <asheplyakov@basealt.ru>
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Date: Mon, 12 Apr 2021 11:48:15 +0400
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Subject: Re: [devel] OpenVZ/p8, bin/tar: Too many levels of symbolic links
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Добрый день!

On 12.04.2021 10:59, Sergey Afonin wrote:
> On Tuesday 30 March 2021, Dmitry V. Levin wrote:
> 
>> Интересно, на каком системном вызове это происходит, и как он выглядит?
> 
> Как раз подвернулся архив, на котором при распаковке вылезло:
> 
> В strace это выглядит как-то так:
> 
> newfstatat(AT_FDCWD, "inn/.git/hooks/pre-rebase.sample", {st_mode=S_IFREG|000, st_size=0, ...}, AT_SYMLINK_NOFOLLOW) = 0
> unlinkat(AT_FDCWD, "inn/.git/hooks/pre-rebase.sample", 0) = 0
> symlinkat("/usr/share/git-core/hooks/pre-rebase", AT_FDCWD, "inn/.git/hooks/pre-rebase.sample") = > utimensat(AT_FDCWD, "inn/.git/hooks/pre-rebase.sample", [UTIME_OMIT, {tv_sec=1618208993, tv_nsec=0} /* 2021-04-12T06:29:53+0000 */], AT_SYMLINK_NOFOLLOW) = 0
> newfstatat(AT_FDCWD, "inn/.git/hooks/pre-rebase.sample", {st_mode=S_IFLNK|0777, st_size=36, ...}, AT_SYMLINK_NOFOLLOW) = 0
> openat(AT_FDCWD, "inn/.git/hooks/pre-rebase.sample", O_RDONLY|O_NOFOLLOW|O_CLOEXEC|O_PATH) = -1 ELOOP (Too many levels of symbolic links)

Сделали симлинк inn/.git/hooks/pre-rebase.sample (на /usr/share/git-core/hooks/pre-rebase).
И тут же пытаемся открыть с флагом O_NOFOLLOW.

O_NOFOLLOW
              If the trailing component (i.e., basename) of pathname is  a  symbolic  link,
              then  the open fails, with the error ELOOP.  Symbolic links in earlier compo‐
              nents of the pathname will still be followed.  (Note  that  the  ELOOP  error
              that  can occur in this case is indistinguishable from the case where an open
              fails because there are too many symbolic links found while resolving  compo‐
              nents in the prefix part of the pathname.)


Работает, как задокументировано.