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Commit 1c327d96 authored by David Jeffery's avatar David Jeffery Committed by J. Bruce Fields
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lockd: protect nlm_blocked access in nlmsvc_retry_blocked



In nlmsvc_retry_blocked, the check that the list is non-empty and acquiring
the pointer of the first entry is unprotected by any lock.  This allows a rare
race condition when there is only one entry on the list.  A function such as
nlmsvc_grant_callback() can be called, which will temporarily remove the entry
from the list.  Between the list_empty() and list_entry(),the list may become
empty, causing an invalid pointer to be used as an nlm_block, leading to a
possible crash.

This patch adds the nlm_block_lock around these calls to prevent concurrent
use of the nlm_blocked list.

This was a regression introduced by
f904be9c  "lockd: Mostly remove BKL from
the server".

Cc: Bryan Schumaker <bjschuma@netapp.com>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarDavid Jeffery <djeffery@redhat.com>
Signed-off-by: default avatarJ. Bruce Fields <bfields@redhat.com>
parent d1091481
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