Description of problem: In several places, an epoll fd can call another file's ->f_op->poll() method with ep->mtx held. This is in general unsafe, because that other file could itself be an epoll fd that contains the original epoll fd. The code defends against this possibility in its own ->poll() method using ep_call_nested, but there are several other unsafe calls to ->poll elsewhere that can be made to deadlock. For example, the following simple program causes the call in ep_insert recursively call the original fd's ->poll, leading to deadlock References: https://lkml.org/lkml/2011/2/5/220 http://seclists.org/oss-sec/2011/q1/337 Upstream commit: http://git.kernel.org/linus/22bacca48a1755f79b7e0f192ddb9fbb7fc6e64e Acknowledgements: Red Hat would like to thank Nelson Elhage for reporting this issue.
Upstream commit: http://git.kernel.org/linus/22bacca48a1755f79b7e0f192ddb9fbb7fc6e64e
This issue has been addressed in following products: MRG for RHEL-5 Via RHSA-2011:0500 https://rhn.redhat.com/errata/RHSA-2011-0500.html
This issue has been addressed in following products: Red Hat Enterprise Linux 6 Via RHSA-2011:0542 https://rhn.redhat.com/errata/RHSA-2011-0542.html
Statement: This issue does not affect the Linux kernel as shipped with Red Hat Enterprise Linux 4 and 5. This was addressed in Red Hat Enterprise Linux 6 and Red Hat Enterprise MRG via https://rhn.redhat.com/errata/RHSA-2011-0542.html and https://rhn.redhat.com/errata/RHSA-2011-0500.html.
This issue has been addressed in following products: Red Hat Enterprise Linux 6.0.Z - Server Only Via RHSA-2011:0883 https://rhn.redhat.com/errata/RHSA-2011-0883.html