diff options
| author | Eric W. Biederman | 2012-12-21 20:38:00 -0800 |
|---|---|---|
| committer | Eric W. Biederman | 2012-12-25 16:23:12 -0800 |
| commit | dfb2ea45becb198beeb75350d0b7b7ad9076a38f (patch) | |
| tree | 7efa7f2073cf0e0ce085dd78adea855df3033d50 | |
| parent | c876ad7682155958d0c9c27afe9017925c230d64 (diff) | |
proc: Allow proc_free_inum to be called from any context
While testing the pid namespace code I hit this nasty warning.
[ 176.262617] ------------[ cut here ]------------
[ 176.263388] WARNING: at /home/eric/projects/linux/linux-userns-devel/kernel/softirq.c:160 local_bh_enable_ip+0x7a/0xa0()
[ 176.265145] Hardware name: Bochs
[ 176.265677] Modules linked in:
[ 176.266341] Pid: 742, comm: bash Not tainted 3.7.0userns+ #18
[ 176.266564] Call Trace:
[ 176.266564] [<ffffffff810a539f>] warn_slowpath_common+0x7f/0xc0
[ 176.266564] [<ffffffff810a53fa>] warn_slowpath_null+0x1a/0x20
[ 176.266564] [<ffffffff810ad9ea>] local_bh_enable_ip+0x7a/0xa0
[ 176.266564] [<ffffffff819308c9>] _raw_spin_unlock_bh+0x19/0x20
[ 176.266564] [<ffffffff8123dbda>] proc_free_inum+0x3a/0x50
[ 176.266564] [<ffffffff8111d0dc>] free_pid_ns+0x1c/0x80
[ 176.266564] [<ffffffff8111d195>] put_pid_ns+0x35/0x50
[ 176.266564] [<ffffffff810c608a>] put_pid+0x4a/0x60
[ 176.266564] [<ffffffff8146b177>] tty_ioctl+0x717/0xc10
[ 176.266564] [<ffffffff810aa4d5>] ? wait_consider_task+0x855/0xb90
[ 176.266564] [<ffffffff81086bf9>] ? default_spin_lock_flags+0x9/0x10
[ 176.266564] [<ffffffff810cab0a>] ? remove_wait_queue+0x5a/0x70
[ 176.266564] [<ffffffff811e37e8>] do_vfs_ioctl+0x98/0x550
[ 176.266564] [<ffffffff810b8a0f>] ? recalc_sigpending+0x1f/0x60
[ 176.266564] [<ffffffff810b9127>] ? __set_task_blocked+0x37/0x80
[ 176.266564] [<ffffffff810ab95b>] ? sys_wait4+0xab/0xf0
[ 176.266564] [<ffffffff811e3d31>] sys_ioctl+0x91/0xb0
[ 176.266564] [<ffffffff810a95f0>] ? task_stopped_code+0x50/0x50
[ 176.266564] [<ffffffff81939199>] system_call_fastpath+0x16/0x1b
[ 176.266564] ---[ end trace 387af88219ad6143 ]---
It turns out that spin_unlock_bh(proc_inum_lock) is not safe when
put_pid is called with another spinlock held and irqs disabled.
For now take the easy path and use spin_lock_irqsave(proc_inum_lock)
in proc_free_inum and spin_loc_irq in proc_alloc_inum(proc_inum_lock).
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
| -rw-r--r-- | fs/proc/generic.c | 13 |
1 files changed, 7 insertions, 6 deletions
diff --git a/fs/proc/generic.c b/fs/proc/generic.c index e064f562b1f7..76ddae83daa5 100644 --- a/fs/proc/generic.c +++ b/fs/proc/generic.c @@ -352,18 +352,18 @@ retry: if (!ida_pre_get(&proc_inum_ida, GFP_KERNEL)) return -ENOMEM; - spin_lock_bh(&proc_inum_lock); + spin_lock_irq(&proc_inum_lock); error = ida_get_new(&proc_inum_ida, &i); - spin_unlock_bh(&proc_inum_lock); + spin_unlock_irq(&proc_inum_lock); if (error == -EAGAIN) goto retry; else if (error) return error; if (i > UINT_MAX - PROC_DYNAMIC_FIRST) { - spin_lock_bh(&proc_inum_lock); + spin_lock_irq(&proc_inum_lock); ida_remove(&proc_inum_ida, i); - spin_unlock_bh(&proc_inum_lock); + spin_unlock_irq(&proc_inum_lock); return -ENOSPC; } *inum = PROC_DYNAMIC_FIRST + i; @@ -372,9 +372,10 @@ retry: void proc_free_inum(unsigned int inum) { - spin_lock_bh(&proc_inum_lock); + unsigned long flags; + spin_lock_irqsave(&proc_inum_lock, flags); ida_remove(&proc_inum_ida, inum - PROC_DYNAMIC_FIRST); - spin_unlock_bh(&proc_inum_lock); + spin_unlock_irqrestore(&proc_inum_lock, flags); } static void *proc_follow_link(struct dentry *dentry, struct nameidata *nd) |