4.20-stable review patch. If anyone has any objections, please let me know.
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From: Alexander Shishkin alexander.shishkin@linux.intel.com
commit c18614a1a11276837bdd44403d84d207c9951538 upstream.
Commit c7fd62bc69d0 ("stm class: Introduce framing protocol drivers") adds a bug into the error path of policy creation, that would do a module_put() on a wrong module, if one tried to create a policy for an stm device which already has a policy, using a different protocol. IOW,
| mkdir /config/stp-policy/dummy_stm.0:p_basic.test | mkdir /config/stp-policy/dummy_stm.0:p_sys-t.test # puts "p_basic" | mkdir /config/stp-policy/dummy_stm.0:p_sys-t.test # "p_basic" -> -1
throws:
| general protection fault: 0000 [#1] SMP PTI | CPU: 3 PID: 2887 Comm: mkdir | RIP: 0010:module_put.part.31+0xe/0x90 | Call Trace: | module_put+0x13/0x20 | stm_put_protocol+0x11/0x20 [stm_core] | stp_policy_make+0xf1/0x210 [stm_core] | ? __kmalloc+0x183/0x220 | ? configfs_mkdir+0x10d/0x4c0 | configfs_mkdir+0x169/0x4c0 | vfs_mkdir+0x108/0x1c0 | do_mkdirat+0xe8/0x110 | __x64_sys_mkdir+0x1b/0x20 | do_syscall_64+0x5a/0x140 | entry_SYSCALL_64_after_hwframe+0x44/0xa9
Correct this sad mistake by calling calling 'put' on the correct reference, which happens to match another error path in the same function, so we consolidate the two at the same time.
Signed-off-by: Alexander Shishkin alexander.shishkin@linux.intel.com Fixes: c7fd62bc69d0 ("stm class: Introduce framing protocol drivers") Reported-by: Ammy Yi ammy.yi@intel.com Cc: stable stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/hwtracing/stm/policy.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-)
--- a/drivers/hwtracing/stm/policy.c +++ b/drivers/hwtracing/stm/policy.c @@ -440,10 +440,8 @@ stp_policy_make(struct config_group *gro
stm->policy = kzalloc(sizeof(*stm->policy), GFP_KERNEL); if (!stm->policy) { - mutex_unlock(&stm->policy_mutex); - stm_put_protocol(pdrv); - stm_put_device(stm); - return ERR_PTR(-ENOMEM); + ret = ERR_PTR(-ENOMEM); + goto unlock_policy; }
config_group_init_type_name(&stm->policy->group, name, @@ -458,7 +456,11 @@ unlock_policy: mutex_unlock(&stm->policy_mutex);
if (IS_ERR(ret)) { - stm_put_protocol(stm->pdrv); + /* + * pdrv and stm->pdrv at this point can be quite different, + * and only one of them needs to be 'put' + */ + stm_put_protocol(pdrv); stm_put_device(stm); }