From 592867bfabe2fcb449393ba7eb0de4f972a08c63 Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Tue, 8 Sep 2015 18:00:09 +0200 Subject: [PATCH] ebpf: fix fd refcount leaks related to maps in bpf syscall We may already have gotten a proper fd struct through fdget(), so whenever we return at the end of an map operation, we need to call fdput(). However, each map operation from syscall side first probes CHECK_ATTR() to verify that unused fields in the bpf_attr union are zero. In case of malformed input, we return with error, but the lookup to the map_fd was already performed at that time, so that we return without an corresponding fdput(). Fix it by performing an fdget() only right before bpf_map_get(). The fdget() invocation on maps in the verifier is not affected. Fixes: db20fd2b0108 ("bpf: add lookup/update/delete/iterate methods to BPF maps") Signed-off-by: Daniel Borkmann Acked-by: Alexei Starovoitov Signed-off-by: David S. Miller --- kernel/bpf/syscall.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index dc9b464fefa9..35bac8e8b071 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -155,14 +155,15 @@ static int map_lookup_elem(union bpf_attr *attr) void __user *ukey = u64_to_ptr(attr->key); void __user *uvalue = u64_to_ptr(attr->value); int ufd = attr->map_fd; - struct fd f = fdget(ufd); struct bpf_map *map; void *key, *value, *ptr; + struct fd f; int err; if (CHECK_ATTR(BPF_MAP_LOOKUP_ELEM)) return -EINVAL; + f = fdget(ufd); map = bpf_map_get(f); if (IS_ERR(map)) return PTR_ERR(map); @@ -213,14 +214,15 @@ static int map_update_elem(union bpf_attr *attr) void __user *ukey = u64_to_ptr(attr->key); void __user *uvalue = u64_to_ptr(attr->value); int ufd = attr->map_fd; - struct fd f = fdget(ufd); struct bpf_map *map; void *key, *value; + struct fd f; int err; if (CHECK_ATTR(BPF_MAP_UPDATE_ELEM)) return -EINVAL; + f = fdget(ufd); map = bpf_map_get(f); if (IS_ERR(map)) return PTR_ERR(map); @@ -265,14 +267,15 @@ static int map_delete_elem(union bpf_attr *attr) { void __user *ukey = u64_to_ptr(attr->key); int ufd = attr->map_fd; - struct fd f = fdget(ufd); struct bpf_map *map; + struct fd f; void *key; int err; if (CHECK_ATTR(BPF_MAP_DELETE_ELEM)) return -EINVAL; + f = fdget(ufd); map = bpf_map_get(f); if (IS_ERR(map)) return PTR_ERR(map); @@ -305,14 +308,15 @@ static int map_get_next_key(union bpf_attr *attr) void __user *ukey = u64_to_ptr(attr->key); void __user *unext_key = u64_to_ptr(attr->next_key); int ufd = attr->map_fd; - struct fd f = fdget(ufd); struct bpf_map *map; void *key, *next_key; + struct fd f; int err; if (CHECK_ATTR(BPF_MAP_GET_NEXT_KEY)) return -EINVAL; + f = fdget(ufd); map = bpf_map_get(f); if (IS_ERR(map)) return PTR_ERR(map); -- GitLab