72 lines
3.1 KiB
Diff
72 lines
3.1 KiB
Diff
From 28e1b4326abcc66839c6e21dd410fe983ee83fb3 Mon Sep 17 00:00:00 2001
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From: Felipe Balbi <balbi@ti.com>
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Date: Wed, 2 Sep 2015 08:12:28 -0500
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Subject: [PATCH] security: device_cgroup: fix RCU lockdep splat
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while booting AM437x device, the following splat
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triggered:
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[ 12.005238] ===============================
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[ 12.009749] [ INFO: suspicious RCU usage. ]
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[ 12.014116] 4.2.0-next-20150831 #1154 Not tainted
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[ 12.019050] -------------------------------
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[ 12.023408] security/device_cgroup.c:405 device_cgroup:verify_new_ex called without proper synchronization!
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[ 12.033576] other info that might help us debug this:
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[ 12.041942] rcu_scheduler_active = 1, debug_locks = 0
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[ 12.048796] 4 locks held by systemd/1:
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[ 12.052700] #0: (sb_writers#7){.+.+.+}, at: [<c017af84>] __sb_start_write+0x8c/0xb0
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[ 12.060954] #1: (&of->mutex){+.+.+.}, at: [<c01f1600>] kernfs_fop_write+0x50/0x1b8
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[ 12.069085] #2: (s_active#30){++++.+}, at: [<c01f1608>] kernfs_fop_write+0x58/0x1b8
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[ 12.077310] #3: (devcgroup_mutex){+.+...}, at: [<c0317bfc>] devcgroup_access_write+0x20/0x658
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[ 12.086575] stack backtrace:
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[ 12.091124] CPU: 0 PID: 1 Comm: systemd Not tainted 4.2.0-next-20150831 #1154
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[ 12.098609] Hardware name: Generic AM43 (Flattened Device Tree)
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[ 12.104807] [<c001770c>] (unwind_backtrace) from [<c0013a58>] (show_stack+0x10/0x14)
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[ 12.112924] [<c0013a58>] (show_stack) from [<c034f014>] (dump_stack+0x84/0x9c)
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[ 12.120491] [<c034f014>] (dump_stack) from [<c0317a04>] (verify_new_ex+0xc4/0xdc)
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[ 12.128326] [<c0317a04>] (verify_new_ex) from [<c0317f50>] (devcgroup_access_write+0x374/0x658)
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[ 12.137426] [<c0317f50>] (devcgroup_access_write) from [<c00d2800>] (cgroup_file_write+0x28/0x1bc)
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[ 12.146796] [<c00d2800>] (cgroup_file_write) from [<c01f1670>] (kernfs_fop_write+0xc0/0x1b8)
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[ 12.155620] [<c01f1670>] (kernfs_fop_write) from [<c0177c94>] (__vfs_write+0x1c/0xd8)
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[ 12.163783] [<c0177c94>] (__vfs_write) from [<c0178594>] (vfs_write+0x90/0x16c)
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[ 12.171426] [<c0178594>] (vfs_write) from [<c0178db4>] (SyS_write+0x44/0x9c)
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[ 12.178806] [<c0178db4>] (SyS_write) from [<c000f680>] (ret_fast_syscall+0x0/0x1c)
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Fix it by making sure rcu_read_lock() is held
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around calls to parent_has_perm().
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Signed-off-by: Felipe Balbi <balbi@ti.com>
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---
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security/device_cgroup.c | 7 ++++++-
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1 file changed, 6 insertions(+), 1 deletion(-)
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diff --git a/security/device_cgroup.c b/security/device_cgroup.c
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index 73455089feef..dd77ed206fa4 100644
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--- a/security/device_cgroup.c
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+++ b/security/device_cgroup.c
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@@ -608,6 +608,7 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup,
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int count, rc = 0;
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struct dev_exception_item ex;
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struct dev_cgroup *parent = css_to_devcgroup(devcgroup->css.parent);
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+ int ret;
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if (!capable(CAP_SYS_ADMIN))
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return -EPERM;
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@@ -734,7 +735,11 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup,
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break;
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}
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- if (!parent_has_perm(devcgroup, &ex))
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+ rcu_read_lock();
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+ ret = parent_has_perm(devcgroup, &ex);
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+ rcu_read_unlock();
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+
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+ if (!ret)
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return -EPERM;
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rc = dev_exception_add(devcgroup, &ex);
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break;
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--
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2.4.3
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