| Message ID | 1441199548-29633-1-git-send-email-balbi@ti.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, Sep 2, 2015 at 9:12 AM, Felipe Balbi <balbi@ti.com> wrote: > while booting AM437x device, the following splat > triggered: > > [ 12.005238] =============================== > [ 12.009749] [ INFO: suspicious RCU usage. ] > [ 12.014116] 4.2.0-next-20150831 #1154 Not tainted > [ 12.019050] ------------------------------- > [ 12.023408] security/device_cgroup.c:405 device_cgroup:verify_new_ex called without proper synchronization! > [ 12.033576] other info that might help us debug this: > > [ 12.041942] rcu_scheduler_active = 1, debug_locks = 0 > [ 12.048796] 4 locks held by systemd/1: > [ 12.052700] #0: (sb_writers#7){.+.+.+}, at: [<c017af84>] __sb_start_write+0x8c/0xb0 > [ 12.060954] #1: (&of->mutex){+.+.+.}, at: [<c01f1600>] kernfs_fop_write+0x50/0x1b8 > [ 12.069085] #2: (s_active#30){++++.+}, at: [<c01f1608>] kernfs_fop_write+0x58/0x1b8 > [ 12.077310] #3: (devcgroup_mutex){+.+...}, at: [<c0317bfc>] devcgroup_access_write+0x20/0x658 > [ 12.086575] stack backtrace: > [ 12.091124] CPU: 0 PID: 1 Comm: systemd Not tainted 4.2.0-next-20150831 #1154 > [ 12.098609] Hardware name: Generic AM43 (Flattened Device Tree) > [ 12.104807] [<c001770c>] (unwind_backtrace) from [<c0013a58>] (show_stack+0x10/0x14) > [ 12.112924] [<c0013a58>] (show_stack) from [<c034f014>] (dump_stack+0x84/0x9c) > [ 12.120491] [<c034f014>] (dump_stack) from [<c0317a04>] (verify_new_ex+0xc4/0xdc) > [ 12.128326] [<c0317a04>] (verify_new_ex) from [<c0317f50>] (devcgroup_access_write+0x374/0x658) > [ 12.137426] [<c0317f50>] (devcgroup_access_write) from [<c00d2800>] (cgroup_file_write+0x28/0x1bc) > [ 12.146796] [<c00d2800>] (cgroup_file_write) from [<c01f1670>] (kernfs_fop_write+0xc0/0x1b8) > [ 12.155620] [<c01f1670>] (kernfs_fop_write) from [<c0177c94>] (__vfs_write+0x1c/0xd8) > [ 12.163783] [<c0177c94>] (__vfs_write) from [<c0178594>] (vfs_write+0x90/0x16c) > [ 12.171426] [<c0178594>] (vfs_write) from [<c0178db4>] (SyS_write+0x44/0x9c) > [ 12.178806] [<c0178db4>] (SyS_write) from [<c000f680>] (ret_fast_syscall+0x0/0x1c) > > Fix it by making sure rcu_read_lock() is held > around calls to parent_has_perm(). > > Signed-off-by: Felipe Balbi <balbi@ti.com> This cleared up the splat on all my machines and I don't see any other side effects (even with lockdep enabled). Thanks! Tested-by: Josh Boyer <jwboyer@fedoraproject.org> josh > --- > > Changes since v1: > - move rcu_read_lock/unlock to wrap parent_has_perm() > > security/device_cgroup.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/security/device_cgroup.c b/security/device_cgroup.c > index 73455089feef..dd77ed206fa4 100644 > --- a/security/device_cgroup.c > +++ b/security/device_cgroup.c > @@ -608,6 +608,7 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup, > int count, rc = 0; > struct dev_exception_item ex; > struct dev_cgroup *parent = css_to_devcgroup(devcgroup->css.parent); > + int ret; > > if (!capable(CAP_SYS_ADMIN)) > return -EPERM; > @@ -734,7 +735,11 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup, > break; > } > > - if (!parent_has_perm(devcgroup, &ex)) > + rcu_read_lock(); > + ret = parent_has_perm(devcgroup, &ex); > + rcu_read_unlock(); > + > + if (!ret) > return -EPERM; > rc = dev_exception_add(devcgroup, &ex); > break; > -- > 2.5.0 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
cc'ing Paul. On Wed, Sep 02, 2015 at 08:12:28AM -0500, Felipe Balbi wrote: > while booting AM437x device, the following splat > triggered: > > [ 12.005238] =============================== > [ 12.009749] [ INFO: suspicious RCU usage. ] > [ 12.014116] 4.2.0-next-20150831 #1154 Not tainted > [ 12.019050] ------------------------------- > [ 12.023408] security/device_cgroup.c:405 device_cgroup:verify_new_ex called without proper synchronization! ... > [ 12.128326] [<c0317a04>] (verify_new_ex) from [<c0317f50>] (devcgroup_access_write+0x374/0x658) > [ 12.137426] [<c0317f50>] (devcgroup_access_write) from [<c00d2800>] (cgroup_file_write+0x28/0x1bc) > [ 12.146796] [<c00d2800>] (cgroup_file_write) from [<c01f1670>] (kernfs_fop_write+0xc0/0x1b8) > [ 12.155620] [<c01f1670>] (kernfs_fop_write) from [<c0177c94>] (__vfs_write+0x1c/0xd8) > [ 12.163783] [<c0177c94>] (__vfs_write) from [<c0178594>] (vfs_write+0x90/0x16c) > [ 12.171426] [<c0178594>] (vfs_write) from [<c0178db4>] (SyS_write+0x44/0x9c) > [ 12.178806] [<c0178db4>] (SyS_write) from [<c000f680>] (ret_fast_syscall+0x0/0x1c) This shouldn't be happening because devcgroup_access_write() always grabs devcgroup_mutex. Looking at the log, the culprit seems to be f78f5b90c4ff ("rcu: Rename rcu_lockdep_assert() to RCU_LOCKDEP_WARN()"). It missed the bang for the second test while inverting it, so adding rcu_read_lock() isn't the right fix here. Paul, can you please fix it? Thanks.
diff --git a/security/device_cgroup.c b/security/device_cgroup.c index 73455089feef..dd77ed206fa4 100644 --- a/security/device_cgroup.c +++ b/security/device_cgroup.c @@ -608,6 +608,7 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup, int count, rc = 0; struct dev_exception_item ex; struct dev_cgroup *parent = css_to_devcgroup(devcgroup->css.parent); + int ret; if (!capable(CAP_SYS_ADMIN)) return -EPERM; @@ -734,7 +735,11 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup, break; } - if (!parent_has_perm(devcgroup, &ex)) + rcu_read_lock(); + ret = parent_has_perm(devcgroup, &ex); + rcu_read_unlock(); + + if (!ret) return -EPERM; rc = dev_exception_add(devcgroup, &ex); break;
while booting AM437x device, the following splat triggered: [ 12.005238] =============================== [ 12.009749] [ INFO: suspicious RCU usage. ] [ 12.014116] 4.2.0-next-20150831 #1154 Not tainted [ 12.019050] ------------------------------- [ 12.023408] security/device_cgroup.c:405 device_cgroup:verify_new_ex called without proper synchronization! [ 12.033576] other info that might help us debug this: [ 12.041942] rcu_scheduler_active = 1, debug_locks = 0 [ 12.048796] 4 locks held by systemd/1: [ 12.052700] #0: (sb_writers#7){.+.+.+}, at: [<c017af84>] __sb_start_write+0x8c/0xb0 [ 12.060954] #1: (&of->mutex){+.+.+.}, at: [<c01f1600>] kernfs_fop_write+0x50/0x1b8 [ 12.069085] #2: (s_active#30){++++.+}, at: [<c01f1608>] kernfs_fop_write+0x58/0x1b8 [ 12.077310] #3: (devcgroup_mutex){+.+...}, at: [<c0317bfc>] devcgroup_access_write+0x20/0x658 [ 12.086575] stack backtrace: [ 12.091124] CPU: 0 PID: 1 Comm: systemd Not tainted 4.2.0-next-20150831 #1154 [ 12.098609] Hardware name: Generic AM43 (Flattened Device Tree) [ 12.104807] [<c001770c>] (unwind_backtrace) from [<c0013a58>] (show_stack+0x10/0x14) [ 12.112924] [<c0013a58>] (show_stack) from [<c034f014>] (dump_stack+0x84/0x9c) [ 12.120491] [<c034f014>] (dump_stack) from [<c0317a04>] (verify_new_ex+0xc4/0xdc) [ 12.128326] [<c0317a04>] (verify_new_ex) from [<c0317f50>] (devcgroup_access_write+0x374/0x658) [ 12.137426] [<c0317f50>] (devcgroup_access_write) from [<c00d2800>] (cgroup_file_write+0x28/0x1bc) [ 12.146796] [<c00d2800>] (cgroup_file_write) from [<c01f1670>] (kernfs_fop_write+0xc0/0x1b8) [ 12.155620] [<c01f1670>] (kernfs_fop_write) from [<c0177c94>] (__vfs_write+0x1c/0xd8) [ 12.163783] [<c0177c94>] (__vfs_write) from [<c0178594>] (vfs_write+0x90/0x16c) [ 12.171426] [<c0178594>] (vfs_write) from [<c0178db4>] (SyS_write+0x44/0x9c) [ 12.178806] [<c0178db4>] (SyS_write) from [<c000f680>] (ret_fast_syscall+0x0/0x1c) Fix it by making sure rcu_read_lock() is held around calls to parent_has_perm(). Signed-off-by: Felipe Balbi <balbi@ti.com> --- Changes since v1: - move rcu_read_lock/unlock to wrap parent_has_perm() security/device_cgroup.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)