From: Viktor Malik vmalik@redhat.com
[ Upstream commit 0053f7d39d491b6138d7c526876d13885cbb65f1 ]
The `readlink(path, buf, sizeof(buf))` call reads at most sizeof(buf) bytes and *does not* append null-terminator to buf. With respect to that, fix two pieces in get_fd_type:
1. Change the truncation check to contain sizeof(buf) rather than sizeof(path). 2. Append null-terminator to buf.
Reported by Coverity.
Signed-off-by: Viktor Malik vmalik@redhat.com Signed-off-by: Andrii Nakryiko andrii@kernel.org Reviewed-by: Quentin Monnet qmo@kernel.org Link: https://lore.kernel.org/bpf/20250129071857.75182-1-vmalik@redhat.com Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- tools/bpf/bpftool/common.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/tools/bpf/bpftool/common.c b/tools/bpf/bpftool/common.c index 9b75639434b81..0a764426d9358 100644 --- a/tools/bpf/bpftool/common.c +++ b/tools/bpf/bpftool/common.c @@ -461,10 +461,11 @@ int get_fd_type(int fd) p_err("can't read link type: %s", strerror(errno)); return -1; } - if (n == sizeof(path)) { + if (n == sizeof(buf)) { p_err("can't read link type: path too long!"); return -1; } + buf[n] = '\0';
if (strstr(buf, "bpf-map")) return BPF_OBJ_MAP;