/// PTR_ERR should access the value just tested by IS_ERR //# There can be false positives in the patch case, where it is the call to //# IS_ERR that is wrong. /// // Confidence: High // Copyright: (C) 2012, 2015 Julia Lawall, INRIA. GPLv2. // Copyright: (C) 2012, 2015 Gilles Muller, INRIA. GPLv2. // URL: http://coccinelle.lip6.fr/ // Options: --no-includes --include-headers virtual patch virtual context virtual org virtual report @ok1 exists@ expression x,e; position p; @@ if (IS_ERR(x=e) || ...) { <... PTR_ERR@p(x) ...> } @ok2 exists@ expression x,e1,e2; position p; @@ if (IS_ERR(x) || ...) { <... ( PTR_ERR@p(\(e1 ? e2 : x\|e1 ? x : e2\)) | PTR_ERR@p(x) ) ...> } @r1 depends on patch && !context && !org && !report exists@ expression x,y; position p != {ok1.p,ok2.p}; @@ if (IS_ERR(x) || ...) { ... when any when != IS_ERR(...) ( PTR_ERR(x) | PTR_ERR@p( - y + x ) ) ... when any } // ---------------------------------------------------------------------------- @r1_context depends on !patch && (context || org || report) exists@ position p != {ok1.p,ok2.p}; expression x, y; position j0, j1; @@ if (IS_ERR@j0(x) || ...) { ... when any when != IS_ERR(...) ( PTR_ERR(x) | PTR_ERR@j1@p( y ) ) ... when any } @r1_disj depends on !patch && (context || org || report) exists@ position p != {ok1.p,ok2.p}; expression x, y; position r1_context.j0, r1_context.j1; @@ * if (IS_ERR@j0(x) || ...) { ... when any when != IS_ERR(...) * PTR_ERR@j1@p( y ) ... when any } // ---------------------------------------------------------------------------- @script:python r1_org depends on org@ j0 << r1_context.j0; j1 << r1_context.j1; @@ msg = "inconsistent IS_ERR and PTR_ERR" coccilib.org.print_todo(j0[0], msg) coccilib.org.print_link(j1[0], "") // ---------------------------------------------------------------------------- @script:python r1_report depends on report@ j0 << r1_context.j0; j1 << r1_context.j1; @@ msg = "inconsistent IS_ERR and PTR_ERR on line %s." % (j1[0].line) coccilib.report.print_report(j0[0], msg) fec09e0144dc3341'>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/core/net_namespace.c
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/core/net_namespace.c')