From 4a1b1ac2744694a2ecd66a84bdb1445f4ef24bee Mon Sep 17 00:00:00 2001 From: Jason Gunthorpe Date: Tue, 26 May 2026 12:40:25 -0300 Subject: [PATCH] RDMA/core: Validate the passed in fops for ib_get_ucaps() Sashiko pointed out it is not safe to rely only on the devt because char/block alias so if the user finds a block device with the same dev_t it can masquerade as a ucap cdev fd. Test the f_ops to only accept authentic cdevs. Link: https://patch.msgid.link/r/0-v1-fd9482545e37+1e25-ib_ucaps_fd_ops_jgg@nvidia.com Cc: stable@vger.kernel.org Fixes: 61e51682816d ("RDMA/uverbs: Introduce UCAP (User CAPabilities) API") Signed-off-by: Jason Gunthorpe --- drivers/infiniband/core/ucaps.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) diff --git a/drivers/infiniband/core/ucaps.c b/drivers/infiniband/core/ucaps.c index 948093260dbd..5155ff0e538e 100644 --- a/drivers/infiniband/core/ucaps.c +++ b/drivers/infiniband/core/ucaps.c @@ -82,14 +82,12 @@ static int get_ucap_from_devt(dev_t devt, u64 *idx_mask) static int get_devt_from_fd(unsigned int fd, dev_t *ret_dev) { - struct file *file; + CLASS(fd, f)(fd); - file = fget(fd); - if (!file) + if (fd_empty(f) || fd_file(f)->f_op != &ucaps_cdev_fops) return -EBADF; - *ret_dev = file_inode(file)->i_rdev; - fput(file); + *ret_dev = file_inode(fd_file(f))->i_rdev; return 0; }