net/mlx5: fix leak in sysfs port name translation

[ upstream commit 1296e8d0d0fe74646fbb0339969cf3946f1ce84d ]

getline() may allocate a buffer even though it returns -1:
"""
If  *lineptr  is set to NULL before the call, then getline() will allocate
a buffer for storing the line.  This buffer should be freed by the user
program even if getline() failed.
"""

This leak has been observed on a RHEL8 system with two CX5 PF devices
(no VFs).

ASan reports:
==8899==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 120 byte(s) in 1 object(s) allocated from:
    #0 0x7fe58576aba8 in __interceptor_malloc
	(/lib64/libasan.so.5+0xefba8)
    #1 0x7fe583e866b2 in __getdelim (/lib64/libc.so.6+0x886b2)
    #2 0x327bd23 in mlx5_sysfs_switch_info
	../drivers/net/mlx5/linux/mlx5_ethdev_os.c:1084
    #3 0x3271f86 in mlx5_os_pci_probe_pf
	../drivers/net/mlx5/linux/mlx5_os.c:2282
    #4 0x3273c83 in mlx5_os_pci_probe
	../drivers/net/mlx5/linux/mlx5_os.c:2497
    #5 0x327475f in mlx5_os_net_probe
	../drivers/net/mlx5/linux/mlx5_os.c:2578
    #6 0xc6eac7 in drivers_probe
	../drivers/common/mlx5/mlx5_common.c:937
    #7 0xc6f150 in mlx5_common_dev_probe
	../drivers/common/mlx5/mlx5_common.c:1027
    #8 0xc8ef80 in mlx5_common_pci_probe
	../drivers/common/mlx5/mlx5_common_pci.c:168
    #9 0xc21b67 in rte_pci_probe_one_driver
	../drivers/bus/pci/pci_common.c:312
    #10 0xc2224c in pci_probe_all_drivers
	../drivers/bus/pci/pci_common.c:396
    #11 0xc222f4 in pci_probe ../drivers/bus/pci/pci_common.c:423
    #12 0xb71fff in rte_bus_probe ../lib/eal/common/eal_common_bus.c:78
    #13 0xbe6888 in rte_eal_init ../lib/eal/linux/eal.c:1300
    #14 0x5ec717 in main ../app/test-pmd/testpmd.c:4515
    #15 0x7fe583e38d84 in __libc_start_main (/lib64/libc.so.6+0x3ad84)

As far as why getline() errors, strace gives a hint:
8516  openat(AT_FDCWD, "/sys/class/net/enp130s0f0/phys_port_name",
	O_RDONLY) = 34
8516  fstat(34, {st_mode=S_IFREG|0444, st_size=4096, ...}) = 0
8516  read(34, 0x621000098900, 4096)    = -1 EOPNOTSUPP (Operation
	not supported)

Fixes: f8a226ed65fa ("net/mlx5: fix sysfs port name translation")

Signed-off-by: David Marchand <david.marchand@redhat.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>

drivers/net/mlx5/linux/mlx5_ethdev_os.c

@@ -1122,6 +1122,7 @@ mlx5_sysfs_switch_info(unsigned int ifindex, struct mlx5_switch_info *info)
 
 		line_size = getline(&port_name, &port_name_size, file);
 		if (line_size < 0) {
+			free(port_name);
 			fclose(file);
 			rte_errno = errno;
 			return -rte_errno;