bpf: Add __force annotations to silence sparse warnings

Add __force annotations to casts that convert between __user and kernel
address spaces. These casts are intentional:

- In bpf_send_signal_common(), the value is stored in si_value.sival_ptr
  which is typed as void __user *, but the value comes from a BPF
  program parameter.

- In the bpf_*_dynptr() kfuncs, user pointers are cast to const void *
  before being passed to copy helper functions that correctly handle
  the user address space through copy_from_user variants.

Without __force, sparse reports:
  warning: cast removes address space '__user' of expression

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20260115184509.3585759-1-mykyta.yatsenko5@gmail.com

Closes: https://lore.kernel.org/oe-kbuild-all/202601131740.6C3BdBaB-lkp@intel.com/

1 files changed, 7 insertions, 7 deletions

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 3a17f79b20c2..f73e08c223b5 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -830,7 +830,7 @@ static int bpf_send_signal_common(u32 sig, enum pid_type type, struct task_struc
 		info.si_code = SI_KERNEL;
 		info.si_pid = 0;
 		info.si_uid = 0;
-		info.si_value.sival_ptr = (void *)(unsigned long)value;
+		info.si_value.sival_ptr = (void __user __force *)(unsigned long)value;
 		siginfo = &info;
 	}
 
@@ -3518,7 +3518,7 @@ __bpf_kfunc int bpf_send_signal_task(struct task_struct *task, int sig, enum pid
 __bpf_kfunc int bpf_probe_read_user_dynptr(struct bpf_dynptr *dptr, u64 off,
 					   u64 size, const void __user *unsafe_ptr__ign)
 {
-	return __bpf_dynptr_copy(dptr, off, size, (const void *)unsafe_ptr__ign,
+	return __bpf_dynptr_copy(dptr, off, size, (const void __force *)unsafe_ptr__ign,
 				 copy_user_data_nofault, NULL);
 }
 
@@ -3532,7 +3532,7 @@ __bpf_kfunc int bpf_probe_read_kernel_dynptr(struct bpf_dynptr *dptr, u64 off,
 __bpf_kfunc int bpf_probe_read_user_str_dynptr(struct bpf_dynptr *dptr, u64 off,
 					       u64 size, const void __user *unsafe_ptr__ign)
 {
-	return __bpf_dynptr_copy_str(dptr, off, size, (const void *)unsafe_ptr__ign,
+	return __bpf_dynptr_copy_str(dptr, off, size, (const void __force *)unsafe_ptr__ign,
 				     copy_user_str_nofault, NULL);
 }
 
@@ -3546,14 +3546,14 @@ __bpf_kfunc int bpf_probe_read_kernel_str_dynptr(struct bpf_dynptr *dptr, u64 of
 __bpf_kfunc int bpf_copy_from_user_dynptr(struct bpf_dynptr *dptr, u64 off,
 					  u64 size, const void __user *unsafe_ptr__ign)
 {
-	return __bpf_dynptr_copy(dptr, off, size, (const void *)unsafe_ptr__ign,
+	return __bpf_dynptr_copy(dptr, off, size, (const void __force *)unsafe_ptr__ign,
 				 copy_user_data_sleepable, NULL);
 }
 
 __bpf_kfunc int bpf_copy_from_user_str_dynptr(struct bpf_dynptr *dptr, u64 off,
 					      u64 size, const void __user *unsafe_ptr__ign)
 {
-	return __bpf_dynptr_copy_str(dptr, off, size, (const void *)unsafe_ptr__ign,
+	return __bpf_dynptr_copy_str(dptr, off, size, (const void __force *)unsafe_ptr__ign,
 				     copy_user_str_sleepable, NULL);
 }
 
@@ -3561,7 +3561,7 @@ __bpf_kfunc int bpf_copy_from_user_task_dynptr(struct bpf_dynptr *dptr, u64 off,
 					       u64 size, const void __user *unsafe_ptr__ign,
 					       struct task_struct *tsk)
 {
-	return __bpf_dynptr_copy(dptr, off, size, (const void *)unsafe_ptr__ign,
+	return __bpf_dynptr_copy(dptr, off, size, (const void __force *)unsafe_ptr__ign,
 				 copy_user_data_sleepable, tsk);
 }
 
@@ -3569,7 +3569,7 @@ __bpf_kfunc int bpf_copy_from_user_task_str_dynptr(struct bpf_dynptr *dptr, u64
 						   u64 size, const void __user *unsafe_ptr__ign,
 						   struct task_struct *tsk)
 {
-	return __bpf_dynptr_copy_str(dptr, off, size, (const void *)unsafe_ptr__ign,
+	return __bpf_dynptr_copy_str(dptr, off, size, (const void __force *)unsafe_ptr__ign,
 				     copy_user_str_sleepable, tsk);
 }