diff options
Diffstat (limited to 'include/linux/rseq_entry.h')
| -rw-r--r-- | include/linux/rseq_entry.h | 89 |
1 files changed, 89 insertions, 0 deletions
diff --git a/include/linux/rseq_entry.h b/include/linux/rseq_entry.h index fb53a6ff05d7..37444e80fd45 100644 --- a/include/linux/rseq_entry.h +++ b/include/linux/rseq_entry.h @@ -75,6 +75,7 @@ DECLARE_STATIC_KEY_MAYBE(CONFIG_RSEQ_DEBUG_DEFAULT_ENABLE, rseq_debug_enabled); #endif bool rseq_debug_update_user_cs(struct task_struct *t, struct pt_regs *regs, unsigned long csaddr); +bool rseq_debug_validate_ids(struct task_struct *t); static __always_inline void rseq_note_user_irq_entry(void) { @@ -194,6 +195,43 @@ efault: return false; } +/* + * On debug kernels validate that user space did not mess with it if the + * debug branch is enabled. + */ +bool rseq_debug_validate_ids(struct task_struct *t) +{ + struct rseq __user *rseq = t->rseq.usrptr; + u32 cpu_id, uval, node_id; + + /* + * On the first exit after registering the rseq region CPU ID is + * RSEQ_CPU_ID_UNINITIALIZED and node_id in user space is 0! + */ + node_id = t->rseq.ids.cpu_id != RSEQ_CPU_ID_UNINITIALIZED ? + cpu_to_node(t->rseq.ids.cpu_id) : 0; + + scoped_user_read_access(rseq, efault) { + unsafe_get_user(cpu_id, &rseq->cpu_id_start, efault); + if (cpu_id != t->rseq.ids.cpu_id) + goto die; + unsafe_get_user(uval, &rseq->cpu_id, efault); + if (uval != cpu_id) + goto die; + unsafe_get_user(uval, &rseq->node_id, efault); + if (uval != node_id) + goto die; + unsafe_get_user(uval, &rseq->mm_cid, efault); + if (uval != t->rseq.ids.mm_cid) + goto die; + } + return true; +die: + t->rseq.event.fatal = true; +efault: + return false; +} + #endif /* RSEQ_BUILD_SLOW_PATH */ /* @@ -279,6 +317,57 @@ efault: return false; } +/* + * Updates CPU ID, Node ID and MM CID and reads the critical section + * address, when @csaddr != NULL. This allows to put the ID update and the + * read under the same uaccess region to spare a separate begin/end. + * + * As this is either invoked from a C wrapper with @csaddr = NULL or from + * the fast path code with a valid pointer, a clever compiler should be + * able to optimize the read out. Spares a duplicate implementation. + * + * Returns true, if the operation was successful, false otherwise. + * + * In the failure case task::rseq_event::fatal is set when invalid data + * was found on debug kernels. It's clear when the failure was an unresolved page + * fault. + * + * If inlined into the exit to user path with interrupts disabled, the + * caller has to protect against page faults with pagefault_disable(). + * + * In preemptible task context this would be counterproductive as the page + * faults could not be fully resolved. As a consequence unresolved page + * faults in task context are fatal too. + */ +static rseq_inline +bool rseq_set_ids_get_csaddr(struct task_struct *t, struct rseq_ids *ids, + u32 node_id, u64 *csaddr) +{ + struct rseq __user *rseq = t->rseq.usrptr; + + if (static_branch_unlikely(&rseq_debug_enabled)) { + if (!rseq_debug_validate_ids(t)) + return false; + } + + scoped_user_rw_access(rseq, efault) { + unsafe_put_user(ids->cpu_id, &rseq->cpu_id_start, efault); + unsafe_put_user(ids->cpu_id, &rseq->cpu_id, efault); + unsafe_put_user(node_id, &rseq->node_id, efault); + unsafe_put_user(ids->mm_cid, &rseq->mm_cid, efault); + if (csaddr) + unsafe_get_user(*csaddr, &rseq->rseq_cs, efault); + } + + /* Cache the new values */ + t->rseq.ids.cpu_cid = ids->cpu_cid; + rseq_stat_inc(rseq_stats.ids); + rseq_trace_update(t, ids); + return true; +efault: + return false; +} + static __always_inline void rseq_exit_to_user_mode(void) { struct rseq_event *ev = ¤t->rseq.event; |