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libbpf: fix using uninitialized ioctl results 

'channels.max_combined' initialized only on ioctl success and
errno is only valid on ioctl failure.

The code doesn't produce any runtime issues, but makes memory
sanitizers angry:

 Conditional jump or move depends on uninitialised value(s)
    at 0x55C056F: xsk_get_max_queues (xsk.c:336)
    by 0x55C05B2: xsk_create_bpf_maps (xsk.c:354)
    by 0x55C089F: xsk_setup_xdp_prog (xsk.c:447)
    by 0x55C0E57: xsk_socket__create (xsk.c:601)
  Uninitialised value was created by a stack allocation
    at 0x55C04CD: xsk_get_max_queues (xsk.c:318)

Additionally fixed warning on uninitialized bytes in ioctl arguments:

 Syscall param ioctl(SIOCETHTOOL) points to uninitialised byte(s)
    at 0x648D45B: ioctl (in /usr/lib64/libc-2.28.so)
    by 0x55C0546: xsk_get_max_queues (xsk.c:330)
    by 0x55C05B2: xsk_create_bpf_maps (xsk.c:354)
    by 0x55C089F: xsk_setup_xdp_prog (xsk.c:447)
    by 0x55C0E57: xsk_socket__create (xsk.c:601)
  Address 0x1ffefff378 is on thread 1's stack
  in frame #1, created by xsk_get_max_queues (xsk.c:318)
  Uninitialised value was created by a stack allocation
    at 0x55C04CD: xsk_get_max_queues (xsk.c:318)

CC: Magnus Karlsson <magnus.karlsson@intel.com>
Fixes: 1cad078842 ("libbpf: add support for using AF_XDP sockets")
Signed-off-by: Ilya Maximets <i.maximets@samsung.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Ilya Maximets 2019-07-23 15:08:10 +03:00 committed by Alexei Starovoitov
parent 7c8b87f012
commit decb705e01
1 changed files with 3 additions and 4 deletions
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7
tools/lib/bpf/xsk.c
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@ -317,15 +317,14 @@ static int xsk_load_xdp_prog(struct xsk_socket *xsk)
static int xsk_get_max_queues(struct xsk_socket *xsk)
{
struct ethtool_channels channels;
struct ifreq ifr;
struct ethtool_channels channels = { .cmd = ETHTOOL_GCHANNELS };
struct ifreq ifr = {};
int fd, err, ret;
fd = socket(AF_INET, SOCK_DGRAM, 0);
if (fd < 0)
return -errno;
channels.cmd = ETHTOOL_GCHANNELS;
ifr.ifr_data = (void *)&channels;
strncpy(ifr.ifr_name, xsk->ifname, IFNAMSIZ - 1);
ifr.ifr_name[IFNAMSIZ - 1] = '\0';
@ -335,7 +334,7 @@ static int xsk_get_max_queues(struct xsk_socket *xsk)
goto out;
}
if (channels.max_combined == 0 || errno == EOPNOTSUPP)
if (err || channels.max_combined == 0)
/* If the device says it has no channels, then all traffic
* is sent to a single stream, so max queues = 1.
*/