diff options
| -rw-r--r-- | kernel/rseq.c | 60 |
1 files changed, 48 insertions, 12 deletions
diff --git a/kernel/rseq.c b/kernel/rseq.c index a7d81229eda0..b7a1ec327e81 100644 --- a/kernel/rseq.c +++ b/kernel/rseq.c @@ -236,6 +236,29 @@ efault: return -EFAULT; } +/* + * Get the user-space pointer value stored in the 'rseq_cs' field. + */ +static int rseq_get_rseq_cs_ptr_val(struct rseq __user *rseq, u64 *rseq_cs) +{ + if (!rseq_cs) + return -EFAULT; + +#ifdef CONFIG_64BIT + if (get_user(*rseq_cs, &rseq->rseq_cs)) + return -EFAULT; +#else + if (copy_from_user(rseq_cs, &rseq->rseq_cs, sizeof(*rseq_cs))) + return -EFAULT; +#endif + + return 0; +} + +/* + * If the rseq_cs field of 'struct rseq' contains a valid pointer to + * user-space, copy 'struct rseq_cs' from user-space and validate its fields. + */ static int rseq_get_rseq_cs(struct task_struct *t, struct rseq_cs *rseq_cs) { struct rseq_cs __user *urseq_cs; @@ -244,17 +267,16 @@ static int rseq_get_rseq_cs(struct task_struct *t, struct rseq_cs *rseq_cs) u32 sig; int ret; -#ifdef CONFIG_64BIT - if (get_user(ptr, &t->rseq->rseq_cs)) - return -EFAULT; -#else - if (copy_from_user(&ptr, &t->rseq->rseq_cs, sizeof(ptr))) - return -EFAULT; -#endif + ret = rseq_get_rseq_cs_ptr_val(t->rseq, &ptr); + if (ret) + return ret; + + /* If the rseq_cs pointer is NULL, return a cleared struct rseq_cs. */ if (!ptr) { memset(rseq_cs, 0, sizeof(*rseq_cs)); return 0; } + /* Check that the pointer value fits in the user-space process space. */ if (ptr >= TASK_SIZE) return -EINVAL; urseq_cs = (struct rseq_cs __user *)(unsigned long)ptr; @@ -330,7 +352,7 @@ static int rseq_need_restart(struct task_struct *t, u32 cs_flags) return !!event_mask; } -static int clear_rseq_cs(struct task_struct *t) +static int clear_rseq_cs(struct rseq __user *rseq) { /* * The rseq_cs field is set to NULL on preemption or signal @@ -341,9 +363,9 @@ static int clear_rseq_cs(struct task_struct *t) * Set rseq_cs to NULL. */ #ifdef CONFIG_64BIT - return put_user(0UL, &t->rseq->rseq_cs); + return put_user(0UL, &rseq->rseq_cs); #else - if (clear_user(&t->rseq->rseq_cs, sizeof(t->rseq->rseq_cs))) + if (clear_user(&rseq->rseq_cs, sizeof(rseq->rseq_cs))) return -EFAULT; return 0; #endif @@ -375,11 +397,11 @@ static int rseq_ip_fixup(struct pt_regs *regs) * Clear the rseq_cs pointer and return. */ if (!in_rseq_cs(ip, &rseq_cs)) - return clear_rseq_cs(t); + return clear_rseq_cs(t->rseq); ret = rseq_need_restart(t, rseq_cs.flags); if (ret <= 0) return ret; - ret = clear_rseq_cs(t); + ret = clear_rseq_cs(t->rseq); if (ret) return ret; trace_rseq_ip_fixup(ip, rseq_cs.start_ip, rseq_cs.post_commit_offset, @@ -453,6 +475,7 @@ SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len, int, flags, u32, sig) { int ret; + u64 rseq_cs; if (flags & RSEQ_FLAG_UNREGISTER) { if (flags & ~RSEQ_FLAG_UNREGISTER) @@ -507,6 +530,19 @@ SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len, return -EINVAL; if (!access_ok(rseq, rseq_len)) return -EFAULT; + + /* + * If the rseq_cs pointer is non-NULL on registration, clear it to + * avoid a potential segfault on return to user-space. The proper thing + * to do would have been to fail the registration but this would break + * older libcs that reuse the rseq area for new threads without + * clearing the fields. + */ + if (rseq_get_rseq_cs_ptr_val(rseq, &rseq_cs)) + return -EFAULT; + if (rseq_cs && clear_rseq_cs(rseq)) + return -EFAULT; + #ifdef CONFIG_DEBUG_RSEQ /* * Initialize the in-kernel rseq fields copy for validation of |