Messages in this thread Patch in this message | | | Date | Sun, 17 Feb 2013 12:03:16 +0800 | From | Li Zefan <> | Subject | [PATCH 1/2] Revert "cgroup: fix cgroup_path() vs rename() race" |
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This reverts commit 299772fab304ab3a36b22b5d28ed81f9408972e7
Sasha reported this:
[ 313.262599] ====================================================== [ 313.271340] [ INFO: HARDIRQ-safe -> HARDIRQ-unsafe lock order detected ] [ 313.277542] 3.8.0-rc6-next-20130208-sasha-00028-ge4e162d #278 Tainted: G W [ 313.277542] ------------------------------------------------------ [ 313.277542] kworker/u:3/4490 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire: [ 313.277542] (rename_lock){+.+...}, at: [<ffffffff812a11f9>] dentry_path_raw+0x29/0x70 [ 313.277542] [ 313.277542] and this task is already holding: [ 313.277542] (&(&q->__queue_lock)->rlock){-.-...}, at: [<ffffffff819e78f3>] put_io_context_active+0x63/0x100 [ 313.277542] which would create a new lock dependency: [ 313.277542] (&(&q->__queue_lock)->rlock){-.-...} -> (rename_lock){+.+...} [ 313.277542] [ 313.277542] but this new dependency connects a HARDIRQ-irq-safe lock: [ 313.277542] (&(&q->__queue_lock)->rlock){-.-...}
dentry_path_raw() grabs rename_lock and dentry->d_lock without disabling irqs, which means cgroup_path() can't be called if the caller has already held a spinlock with irq disabled.
Reported-by: Sasha Levin <levinsasha928@gmail.com> Signed-off-by: Li Zefan <lizefan@huawei.com> --- kernel/cgroup.c | 22 +++++++++++++++++++--- 1 file changed, 19 insertions(+), 3 deletions(-)
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 776ff75..5d4c92e 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -1792,10 +1792,26 @@ int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen) return 0; } - start = dentry_path_raw(dentry, buf, buflen); - if (IS_ERR(start)) - return PTR_ERR(start); + start = buf + buflen - 1; + *start = '\0'; + for (;;) { + int len = dentry->d_name.len; + + if ((start -= len) < buf) + return -ENAMETOOLONG; + memcpy(start, dentry->d_name.name, len); + cgrp = cgrp->parent; + if (!cgrp) + break; + + dentry = cgrp->dentry; + if (!cgrp->parent) + continue; + if (--start < buf) + return -ENAMETOOLONG; + *start = '/'; + } memmove(buf, start, buf + buflen - start); return 0; } -- 1.8.0.2
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