From e6bd18f57aad1a2d1ef40e646d03ed0f2515c9e3 Mon Sep 17 00:00:00 2001 From: Jason Gunthorpe Date: Sun, 10 Apr 2016 19:13:13 -0600 Subject: IB/security: Restrict use of the write() interface The drivers/infiniband stack uses write() as a replacement for bi-directional ioctl(). This is not safe. There are ways to trigger write calls that result in the return structure that is normally written to user space being shunted off to user specified kernel memory instead. For the immediate repair, detect and deny suspicious accesses to the write API. For long term, update the user space libraries and the kernel API to something that doesn't present the same security vulnerabilities (likely a structured ioctl() interface). The impacted uAPI interfaces are generally only available if hardware from drivers/infiniband is installed in the system. Reported-by: Jann Horn Signed-off-by: Linus Torvalds Signed-off-by: Jason Gunthorpe [ Expanded check to all known write() entry points ] Cc: stable@vger.kernel.org Signed-off-by: Doug Ledford --- include/rdma/ib.h | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) (limited to 'include') diff --git a/include/rdma/ib.h b/include/rdma/ib.h index cf8f9e700e48..a6b93706b0fc 100644 --- a/include/rdma/ib.h +++ b/include/rdma/ib.h @@ -34,6 +34,7 @@ #define _RDMA_IB_H #include +#include struct ib_addr { union { @@ -86,4 +87,19 @@ struct sockaddr_ib { __u64 sib_scope_id; }; +/* + * The IB interfaces that use write() as bi-directional ioctl() are + * fundamentally unsafe, since there are lots of ways to trigger "write()" + * calls from various contexts with elevated privileges. That includes the + * traditional suid executable error message writes, but also various kernel + * interfaces that can write to file descriptors. + * + * This function provides protection for the legacy API by restricting the + * calling context. + */ +static inline bool ib_safe_file_access(struct file *filp) +{ + return filp->f_cred == current_cred() && segment_eq(get_fs(), USER_DS); +} + #endif /* _RDMA_IB_H */ -- cgit v1.2.3