From cfc1ba8fbc885986144ab5e18f5c6b12fef9bb87 Mon Sep 17 00:00:00 2001 From: Jason Gunthorpe Date: Sun, 10 Apr 2016 19:13:13 -0600 Subject: [PATCH] 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 CVE-2016-4565 Orabug: 23276449 (cherry-pick from e6bd18f57aad1a2d1ef40e646d03ed0f2515c9e3) Signed-off-by: Santosh Shilimkar --- drivers/infiniband/core/ucm.c | 4 ++++ drivers/infiniband/core/ucma.c | 3 +++ drivers/infiniband/core/uverbs_main.c | 7 ++++++- drivers/infiniband/hw/qib/qib_file_ops.c | 5 +++++ include/rdma/ib.h | 16 ++++++++++++++++ 5 files changed, 34 insertions(+), 1 deletion(-) diff --git a/drivers/infiniband/core/ucm.c b/drivers/infiniband/core/ucm.c index f2f63933e8a9..5befec118a18 100644 --- a/drivers/infiniband/core/ucm.c +++ b/drivers/infiniband/core/ucm.c @@ -48,6 +48,7 @@ #include +#include #include #include #include @@ -1104,6 +1105,9 @@ static ssize_t ib_ucm_write(struct file *filp, const char __user *buf, struct ib_ucm_cmd_hdr hdr; ssize_t result; + if (WARN_ON_ONCE(!ib_safe_file_access(filp))) + return -EACCES; + if (len < sizeof(hdr)) return -EINVAL; diff --git a/drivers/infiniband/core/ucma.c b/drivers/infiniband/core/ucma.c index 45d67e9228d7..81dd84d0b68b 100644 --- a/drivers/infiniband/core/ucma.c +++ b/drivers/infiniband/core/ucma.c @@ -1487,6 +1487,9 @@ static ssize_t ucma_write(struct file *filp, const char __user *buf, struct rdma_ucm_cmd_hdr hdr; ssize_t ret; + if (WARN_ON_ONCE(!ib_safe_file_access(filp))) + return -EACCES; + if (len < sizeof(hdr)) return -EINVAL; diff --git a/drivers/infiniband/core/uverbs_main.c b/drivers/infiniband/core/uverbs_main.c index 229772bb4050..4442a8aedf81 100644 --- a/drivers/infiniband/core/uverbs_main.c +++ b/drivers/infiniband/core/uverbs_main.c @@ -48,6 +48,8 @@ #include +#include + #include "uverbs.h" MODULE_AUTHOR("Roland Dreier"); @@ -689,7 +691,10 @@ static ssize_t ib_uverbs_write(struct file *filp, const char __user *buf, struct ib_uverbs_cmd_hdr hdr; __u32 flags; - if (count < sizeof(hdr)) { + if (WARN_ON_ONCE(!ib_safe_file_access(filp))) + return -EACCES; + + if (count < sizeof hdr) { pr_debug("ib_uverbs_write: header too short\n"); return -EINVAL; } diff --git a/drivers/infiniband/hw/qib/qib_file_ops.c b/drivers/infiniband/hw/qib/qib_file_ops.c index 725881890c4a..619154ec8249 100644 --- a/drivers/infiniband/hw/qib/qib_file_ops.c +++ b/drivers/infiniband/hw/qib/qib_file_ops.c @@ -45,6 +45,8 @@ #include #include +#include + #include "qib.h" #include "qib_common.h" #include "qib_user_sdma.h" @@ -2067,6 +2069,9 @@ static ssize_t qib_write(struct file *fp, const char __user *data, ssize_t ret = 0; void *dest; + if (WARN_ON_ONCE(!ib_safe_file_access(fp))) + return -EACCES; + if (count < sizeof(cmd.type)) { ret = -EINVAL; goto bail; 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 */ -- 2.50.1