CVE-2026-97993vhost-vdpa: don't install the eventfd_ctx_fdget() error in config_ctx

Official description

In the Linux kernel, the following vulnerability has been resolved: vhost-vdpa: don't install the eventfd_ctx_fdget() error in config_ctx vhost_vdpa_set_config_call() swaps the eventfd_ctx_fdget() return value into v->config_ctx before checking it, so on failure the field briefly holds an ERR_PTR: ctx = fd == VHOST_FILE_UNBIND ? NULL : eventfd_ctx_fdget(fd); swap(ctx, v->config_ctx); if (!IS_ERR_OR_NULL(ctx)) eventfd_ctx_put(ctx); if (IS_ERR(v->config_ctx)) { long ret = PTR_ERR(v->config_ctx); v->config_ctx = NULL; return ret; } Commit 0bde59c1723a ("vhost-vdpa: set v->config_ctx to NULL if eventfd_ctx_fdget() fails") added that clearing, and spelled out the invariant the rest of the file relies on: "we consider 'v->config_ctx' valid if it is not NULL". The window between the swap and the clearing still breaks it. vhost_vdpa_config_cb() only tests for NULL, so a config interrupt delivered inside the window hands the ERR_PTR to eventfd_signal(). Check the fd before installing it instead. That closes the window and matches how vhost_vring_ioctl() handles the same failure for the vq call fd. It also stops a rejected fd from tearing down a config interrupt that was working: until now the swap replaced the live context and put it, so after an EBADF the device silently stopped delivering config interrupts until userspace installed a new fd.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/e260dc9fbfdae0978e7a8698f977fbb463a657be
• https://git.kernel.org/stable/c/66e73fa18910b39fea0941dea5fe091122240855
• https://git.kernel.org/stable/c/4fde085eb839fbb39c25cbba5d2a091ded394877
• https://git.kernel.org/stable/c/59fc7c1c6b4d325194ca45352180340092d95098
• https://git.kernel.org/stable/c/388c678639a0cebfd936b3e56c64ac6a371efec2
• https://git.kernel.org/stable/c/65faf9eaa00e408e1406fbcf675c8c8d0e27ff2a
• https://git.kernel.org/stable/c/6b20b40f020bde236f6b8a08ff88d8653261ec2b
• https://git.kernel.org/stable/c/e74a9fa50749b9940b4fb13199652325e08d3c4a