Hi Simon, Thanks for you help, i may got it, here is the new commit message: The current IMA ruleset is identified by the variable "ima_rules" that default to "&ima_default_rules". When loading a custom policy for the first time, the variable is updated to "&ima_policy_rules" instead. That update isn't RCU-safe, and deadlocks are possible. Because some functions like ima_match_policy() may loop indefinitely over traversing the "ima_default_rules" as list_for_each_entry_rcu(). When iterating over the default ruleset back to head, value of "&entry->list" is "&ima_default_rules", and "ima_rules" may have been updated to "&ima_policy_rules", the loop condition (&entry->list != ima_rules) stay alway true, traversing doesn't terminate, cause soft lockup and RCU stalls. Introduce a temporary value for "ima_rules" when iterating over the ruleset to avoid the deadlocks. Signed-off-by: liqiong <liqiong@xxxxxxxxxxxx> --- security/integrity/ima/ima_policy.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c index fd5d46e511f1..e92b197bfd3c 100644 --- a/security/integrity/ima/ima_policy.c +++ b/security/integrity/ima/ima_policy.c Thanks liqiong 在 2021年08月26日 17:01, THOBY Simon 写道: > Hi liqiong, > > On 8/26/21 10:15 AM, liqiong wrote: >> Hi Simon, >> >> Thanks for your help, your advice is clear, can i just use it, >> how about this: >> >> >> The current IMA ruleset is identified by the variable "ima_rules", >> and the pointer starts pointing at the list "ima_default_rules". > After reading it again, maybe > "The current IMA ruleset is identified by the variable "ima_rules", > that defaults to "&ima_default_rules".'? > >> When loading a custom policy for the first time, the variable is >> updated to point to the list "ima_policy_rules" instead. That update >> isn't RCU-safe, and deadlocks are possible. > I think what Mimi was trying to say is that you could add the high-level > overview above, but keep the details. Sorry if I wasn't clearer in my > earlier messages. > > Consider re-adding your previous paragraph > """ > As a consequence, when traversing the ruleset, some functions like ima_match_policy() > may loop indefinitely over "ima_default_rules" as list_for_each_entry_rcu() doesn't > terminate (after the update, "ima_rules" no longer points to the list head, so the > loop condition stays always true), causing RCU stalls. > """ > (note: I tweaked it above, feel free to fix it) >> Introduce a temporary value for "ima_rules" when iterating over >> the ruleset to avoid the deadlocks. > ... while keeping this a separate paragraph. > >> >> Signed-off-by: liqiong <liqiong@xxxxxxxxxxxx> >> --- >> security/integrity/ima/ima_policy.c | 17 ++++++++++++----- >> 1 file changed, 12 insertions(+), 5 deletions(-) >> >> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c >> index fd5d46e511f1..e92b197bfd3c 100644 >> --- a/security/integrity/ima/ima_policy.c >> +++ b/security/integrity/ima/ima_policy.c >> >> >> >> Thanks >> >> liqiong
