bpf: Add "bool swap_uptrs" arg to bpf_local_storage_update() and bpf_selem_alloc()

In a later patch, the task local storage will only accept uptr
from the syscall update_elem and will not accept uptr from
the bpf prog. The reason is the bpf prog does not have a way
to provide a valid user space address.

bpf_local_storage_update() and bpf_selem_alloc() are used by
both bpf prog bpf_task_storage_get(BPF_LOCAL_STORAGE_GET_F_CREATE)
and bpf syscall update_elem. "bool swap_uptrs" arg is added
to bpf_local_storage_update() and bpf_selem_alloc() to tell if
it is called by the bpf prog or by the bpf syscall. When
swap_uptrs==true, it is called by the syscall.

The arg is named (swap_)uptrs because the later patch will swap
the uptrs between the newly allocated selem and the user space
provided map_value. It will make error handling easier in case
map->ops->map_update_elem() fails and the caller can decide
if it needs to unpin the uptr in the user space provided
map_value or the bpf_local_storage_update() has already
taken the uptr ownership and will take care of unpinning it also.

Only swap_uptrs==false is passed now. The logic to handle
the true case will be added in a later patch.

Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://lore.kernel.org/r/20241023234759.860539-4-martin.lau@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/kernel/bpf/bpf_task_storage.c b/kernel/bpf/bpf_task_storage.c
index adf6dfe0ba68..45dc3ca334d3 100644
--- a/kernel/bpf/bpf_task_storage.c
+++ b/kernel/bpf/bpf_task_storage.c
@@ -147,7 +147,7 @@ static long bpf_pid_task_storage_update_elem(struct bpf_map *map, void *key,
 	bpf_task_storage_lock();
 	sdata = bpf_local_storage_update(
 		task, (struct bpf_local_storage_map *)map, value, map_flags,
-		GFP_ATOMIC);
+		false, GFP_ATOMIC);
 	bpf_task_storage_unlock();
 
 	err = PTR_ERR_OR_ZERO(sdata);
@@ -219,7 +219,7 @@ static void *__bpf_task_storage_get(struct bpf_map *map,
 	    (flags & BPF_LOCAL_STORAGE_GET_F_CREATE) && nobusy) {
 		sdata = bpf_local_storage_update(
 			task, (struct bpf_local_storage_map *)map, value,
-			BPF_NOEXIST, gfp_flags);
+			BPF_NOEXIST, false, gfp_flags);
 		return IS_ERR(sdata) ? NULL : sdata->data;
 	}