The rseq system call, when invoked with flags of "0" or "RSEQ_FLAG_UNREGISTER" values, expects the rseq_len parameter to be equal to sizeof(struct rseq), which is fixed-size and fixed-layout, specified in uapi linux/rseq.h.
Expecting a fixed size for rseq_len is a design choice that ensures multiple libraries and application defining __rseq_abi in the same process agree on its exact size. Considering that this size is and will always be the same value, there is no point in saving this value within task_struct rseq_len. Remove this field from task_struct. Signed-off-by: Mathieu Desnoyers <[email protected]> CC: "Paul E. McKenney" <[email protected]> CC: Peter Zijlstra <[email protected]> CC: Paul Turner <[email protected]> CC: Thomas Gleixner <[email protected]> CC: Andy Lutomirski <[email protected]> CC: Andi Kleen <[email protected]> CC: Dave Watson <[email protected]> CC: Chris Lameter <[email protected]> CC: Ingo Molnar <[email protected]> CC: "H. Peter Anvin" <[email protected]> CC: Ben Maurer <[email protected]> CC: Steven Rostedt <[email protected]> CC: Josh Triplett <[email protected]> CC: Linus Torvalds <[email protected]> CC: Andrew Morton <[email protected]> CC: Russell King <[email protected]> CC: Catalin Marinas <[email protected]> CC: Will Deacon <[email protected]> CC: Michael Kerrisk <[email protected]> CC: Boqun Feng <[email protected]> CC: [email protected] --- include/linux/sched.h | 4 ---- kernel/rseq.c | 6 ++---- 2 files changed, 2 insertions(+), 8 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index f9b43c989577..e355688fa82c 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1059,7 +1059,6 @@ struct task_struct { #ifdef CONFIG_RSEQ struct rseq __user *rseq; - u32 rseq_len; u32 rseq_sig; /* * RmW on rseq_event_mask must be performed atomically @@ -1852,12 +1851,10 @@ static inline void rseq_fork(struct task_struct *t, unsigned long clone_flags) { if (clone_flags & CLONE_THREAD) { t->rseq = NULL; - t->rseq_len = 0; t->rseq_sig = 0; t->rseq_event_mask = 0; } else { t->rseq = current->rseq; - t->rseq_len = current->rseq_len; t->rseq_sig = current->rseq_sig; t->rseq_event_mask = current->rseq_event_mask; } @@ -1866,7 +1863,6 @@ static inline void rseq_fork(struct task_struct *t, unsigned long clone_flags) static inline void rseq_execve(struct task_struct *t) { t->rseq = NULL; - t->rseq_len = 0; t->rseq_sig = 0; t->rseq_event_mask = 0; } diff --git a/kernel/rseq.c b/kernel/rseq.c index 849afe749131..9424ee90589e 100644 --- a/kernel/rseq.c +++ b/kernel/rseq.c @@ -313,7 +313,7 @@ SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len, /* Unregister rseq for current thread. */ if (current->rseq != rseq || !current->rseq) return -EINVAL; - if (current->rseq_len != rseq_len) + if (rseq_len != sizeof(*rseq)) return -EINVAL; if (current->rseq_sig != sig) return -EPERM; @@ -321,7 +321,6 @@ SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len, if (ret) return ret; current->rseq = NULL; - current->rseq_len = 0; current->rseq_sig = 0; return 0; } @@ -335,7 +334,7 @@ SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len, * the provided address differs from the prior * one. */ - if (current->rseq != rseq || current->rseq_len != rseq_len) + if (current->rseq != rseq || rseq_len != sizeof(*rseq)) return -EINVAL; if (current->rseq_sig != sig) return -EPERM; @@ -353,7 +352,6 @@ SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len, if (!access_ok(rseq, rseq_len)) return -EFAULT; current->rseq = rseq; - current->rseq_len = rseq_len; current->rseq_sig = sig; /* * If rseq was previously inactive, and has just been -- 2.11.0
