/* * Intel MIC Platform Software Stack (MPSS) * * Copyright(c) 2013 Intel Corporation. * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License, version 2, as * published by the Free Software Foundation. * * This program is distributed in the hope that it will be useful, but * WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * General Public License for more details. * * The full GNU General Public License is included in this distribution in * the file called "COPYING". * * Intel MIC User Space Tools. */ #include "mpssd.h" #define PAGE_SIZE 4096 char * readsysfs(char *dir, char *entry) { char filename[PATH_MAX]; char value[PAGE_SIZE]; char *string = NULL; int fd; int len; if (dir == NULL) snprintf(filename, PATH_MAX, "%s/%s", MICSYSFSDIR, entry); else snprintf(filename, PATH_MAX, "%s/%s/%s", MICSYSFSDIR, dir, entry); fd = open(filename, O_RDONLY); if (fd < 0) { mpsslog("Failed to open sysfs entry '%s': %s\n", filename, strerror(errno)); return NULL; } len = read(fd, value, sizeof(value)); if (len < 0) { mpsslog("Failed to read sysfs entry '%s': %s\n", filename, strerror(errno)); goto readsys_ret; } if (len == 0) goto readsys_ret; value[len - 1] = '\0'; string = malloc(strlen(value) + 1); if (string) strcpy(string, value); readsys_ret: close(fd); return string; } int setsysfs(char *dir, char *entry, char *value) { char filename[PATH_MAX]; char *oldvalue; int fd, ret = 0; if (dir == NULL) snprintf(filename, PATH_MAX, "%s/%s", MICSYSFSDIR, entry); else snprintf(filename, PATH_MAX, "%s/%s/%s", MICSYSFSDIR, dir, entry); oldvalue = readsysfs(dir, entry); fd = open(filename, O_RDWR); if (fd < 0) { ret = errno; mpsslog("Failed to open sysfs entry '%s': %s\n", filename, strerror(errno)); goto done; } if (!oldvalue || strcmp(value, oldvalue)) { if (write(fd, value, strlen(value)) < 0) { ret = errno; mpsslog("Failed to write new sysfs entry '%s': %s\n", filename, strerror(errno)); } } close(fd); done: if (oldvalue) free(oldvalue); return ret; } f/net/openvswitch/flow_table.h?h=nds-private-remove&id=966d2b04e070bc040319aaebfec09e0144dc3341'>diff
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authorDouglas Miller <dougmill@linux.vnet.ibm.com>2017-01-28 06:42:20 -0600
committerTejun Heo <tj@kernel.org>2017-01-28 07:49:42 -0500
commit966d2b04e070bc040319aaebfec09e0144dc3341 (patch)
tree4b96156e3d1dd4dfd6039b7c219c9dc4616da52d /net/openvswitch/flow_table.h
parent1b1bc42c1692e9b62756323c675a44cb1a1f9dbd (diff)
percpu-refcount: fix reference leak during percpu-atomic transition
percpu_ref_tryget() and percpu_ref_tryget_live() should return "true" IFF they acquire a reference. But the return value from atomic_long_inc_not_zero() is a long and may have high bits set, e.g. PERCPU_COUNT_BIAS, and the return value of the tryget routines is bool so the reference may actually be acquired but the routines return "false" which results in a reference leak since the caller assumes it does not need to do a corresponding percpu_ref_put(). This was seen when performing CPU hotplug during I/O, as hangs in blk_mq_freeze_queue_wait where percpu_ref_kill (blk_mq_freeze_queue_start) raced with percpu_ref_tryget (blk_mq_timeout_work). Sample stack trace: __switch_to+0x2c0/0x450 __schedule+0x2f8/0x970 schedule+0x48/0xc0 blk_mq_freeze_queue_wait+0x94/0x120 blk_mq_queue_reinit_work+0xb8/0x180 blk_mq_queue_reinit_prepare+0x84/0xa0 cpuhp_invoke_callback+0x17c/0x600 cpuhp_up_callbacks+0x58/0x150 _cpu_up+0xf0/0x1c0 do_cpu_up+0x120/0x150 cpu_subsys_online+0x64/0xe0 device_online+0xb4/0x120 online_store+0xb4/0xc0 dev_attr_store+0x68/0xa0 sysfs_kf_write+0x80/0xb0 kernfs_fop_write+0x17c/0x250 __vfs_write+0x6c/0x1e0 vfs_write+0xd0/0x270 SyS_write+0x6c/0x110 system_call+0x38/0xe0 Examination of the queue showed a single reference (no PERCPU_COUNT_BIAS, and __PERCPU_REF_DEAD, __PERCPU_REF_ATOMIC set) and no requests. However, conditions at the time of the race are count of PERCPU_COUNT_BIAS + 0 and __PERCPU_REF_DEAD and __PERCPU_REF_ATOMIC set. The fix is to make the tryget routines use an actual boolean internally instead of the atomic long result truncated to a int. Fixes: e625305b3907 percpu-refcount: make percpu_ref based on longs instead of ints Link: https://bugzilla.kernel.org/show_bug.cgi?id=190751 Signed-off-by: Douglas Miller <dougmill@linux.vnet.ibm.com> Reviewed-by: Jens Axboe <axboe@fb.com> Signed-off-by: Tejun Heo <tj@kernel.org> Fixes: e625305b3907 ("percpu-refcount: make percpu_ref based on longs instead of ints") Cc: stable@vger.kernel.org # v3.18+
Diffstat (limited to 'net/openvswitch/flow_table.h')