From: Geoffrey McRae <[email protected]> [ Upstream commit 57af162bfc8c05332a28c4d458d246cc46d2746d ]
Some kfd ioctls may not be available depending on the kernel version the user is running, as such we need to report -ENOTTY so userland can determine the cause of the ioctl failure. Signed-off-by: Geoffrey McRae <[email protected]> Acked-by: Alex Deucher <[email protected]> Reviewed-by: Felix Kuehling <[email protected]> Signed-off-by: Alex Deucher <[email protected]> Signed-off-by: Sasha Levin <[email protected]> --- LLM Generated explanations, may be completely bogus: YES - What changed - Unsupported amdkfd ioctls now return -ENOTTY instead of the previous default -EINVAL on two early error paths: - When `_IOC_NR(cmd)` is beyond the table: `nr >= AMDKFD_CORE_IOCTL_COUNT` now sets `retcode = -ENOTTY` before `goto err_i1` (drivers/gpu/drm/amd/amdkfd/kfd_chardev.c:3256). - When the ioctl number is outside the defined KFD command range: the `else` branch after the `(nr >= AMDKFD_COMMAND_START) && (nr < AMDKFD_COMMAND_END)` check now sets `retcode = -ENOTTY` before `goto err_i1` (drivers/gpu/drm/amd/amdkfd/kfd_chardev.c:3270). - Prior to this change, both paths fell through with `retcode` initialized to -EINVAL (drivers/gpu/drm/amd/amdkfd/kfd_chardev.c:3253). - Why it matters - KFD adds ioctls over time; user space built against newer headers may issue an ioctl unknown to an older kernel. Returning -ENOTTY is the canonical “inappropriate ioctl for device/unsupported ioctl” signal, allowing user space to distinguish “unsupported on this kernel” from “bad arguments to a supported ioctl” (which should be -EINVAL). - This aligns KFD’s error semantics with kernel ioctl conventions used elsewhere. For example, DRM core returns -ENOTTY for unsupported ioctl types (drivers/gpu/drm/drm_ioctl.c:782), and many drivers use -ENOTTY to indicate unsupported ioctls. - Scope and risk - Change is small and tightly scoped to `kfd_ioctl` error handling for unsupported commands only (drivers/gpu/drm/amd/amdkfd/kfd_chardev.c:3244). - No architectural changes, no new UAPI or features, and no functional change for supported ioctls. - Potential regression risk is low: only the errno for “unsupported ioctl” changes from -EINVAL to -ENOTTY. Well-behaved user space should treat -ENOTTY (not -EINVAL) as the indicator for an unsupported ioctl. This is correcting an API bug rather than changing intended behavior. - Security impact is nil; control flow and data handling are unchanged. - Stable backport criteria - Fixes a real user-visible bug: ambiguous errno on unsupported ioctls made feature detection and fallback logic in userland unreliable. - Minimal, self-contained patch limited to amdkfd. - No side effects beyond improving errno correctness for unsupported ioctls. - Consistent with prior amdkfd errno cleanups (e.g., “Return proper error code for gws alloc API”) and general kernel ioctl practices. Given these points, this is a good, low-risk candidate for stable backport. drivers/gpu/drm/amd/amdkfd/kfd_chardev.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c b/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c index 828a9ceef1e76..79ed3be63d0dd 100644 --- a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c +++ b/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c @@ -3252,8 +3252,10 @@ static long kfd_ioctl(struct file *filep, unsigned int cmd, unsigned long arg) int retcode = -EINVAL; bool ptrace_attached = false; - if (nr >= AMDKFD_CORE_IOCTL_COUNT) + if (nr >= AMDKFD_CORE_IOCTL_COUNT) { + retcode = -ENOTTY; goto err_i1; + } if ((nr >= AMDKFD_COMMAND_START) && (nr < AMDKFD_COMMAND_END)) { u32 amdkfd_size; @@ -3266,8 +3268,10 @@ static long kfd_ioctl(struct file *filep, unsigned int cmd, unsigned long arg) asize = amdkfd_size; cmd = ioctl->cmd; - } else + } else { + retcode = -ENOTTY; goto err_i1; + } dev_dbg(kfd_device, "ioctl cmd 0x%x (#0x%x), arg 0x%lx\n", cmd, nr, arg); -- 2.51.0
