Validating the abort_ip field of rseq_cs ensures that the kernel don't return to an invalid address when returning to userspace after an abort. I don't fully trust each architecture code to cleanly deal with invalid return addresses.
Validating the range [ start_ip, start_ip + post_commit_offset ] is an extra validation step ensuring that userspace provides valid values to describe the critical section. If validation fails, the process is killed with a segmentation fault. Change the rseq ABI so rseq_cs start_ip, post_commit_offset and abort_ip fields are seen as 64-bit fields by both 32-bit and 64-bit kernels rather that ignoring the 32 upper bits on 32-bit kernels. This ensures we have a consistent behavior for a 32-bit binary executed on 32-bit kernels and in compat mode on 64-bit kernels. 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/uapi/linux/rseq.h | 6 +++--- kernel/rseq.c | 7 +++++-- 2 files changed, 8 insertions(+), 5 deletions(-) diff --git a/include/uapi/linux/rseq.h b/include/uapi/linux/rseq.h index d620fa43756c..519ad6e176d1 100644 --- a/include/uapi/linux/rseq.h +++ b/include/uapi/linux/rseq.h @@ -52,10 +52,10 @@ struct rseq_cs { __u32 version; /* enum rseq_cs_flags */ __u32 flags; - LINUX_FIELD_u32_u64(start_ip); + __u64 start_ip; /* Offset from start_ip. */ - LINUX_FIELD_u32_u64(post_commit_offset); - LINUX_FIELD_u32_u64(abort_ip); + __u64 post_commit_offset; + __u64 abort_ip; } __attribute__((aligned(4 * sizeof(__u64)))); /* diff --git a/kernel/rseq.c b/kernel/rseq.c index 22b6acf1ad63..4ba582046fcd 100644 --- a/kernel/rseq.c +++ b/kernel/rseq.c @@ -128,7 +128,10 @@ static int rseq_get_rseq_cs(struct task_struct *t, struct rseq_cs *rseq_cs) return 0; } urseq_cs = (struct rseq_cs __user *)ptr; - if (copy_from_user(rseq_cs, urseq_cs, sizeof(*rseq_cs))) + if (copy_from_user(rseq_cs, urseq_cs, sizeof(*rseq_cs)) || + rseq_cs->abort_ip >= TASK_SIZE || + rseq_cs->start_ip >= TASK_SIZE || + rseq_cs->start_ip + rseq_cs->post_commit_offset >= TASK_SIZE) return -EFAULT; if (rseq_cs->version > 0) return -EINVAL; @@ -137,7 +140,7 @@ static int rseq_get_rseq_cs(struct task_struct *t, struct rseq_cs *rseq_cs) if (rseq_cs->abort_ip - rseq_cs->start_ip < rseq_cs->post_commit_offset) return -EINVAL; - usig = (u32 __user *)(rseq_cs->abort_ip - sizeof(u32)); + usig = (u32 __user *)(unsigned long)(rseq_cs->abort_ip - sizeof(u32)); ret = get_user(sig, usig); if (ret) return ret; -- 2.11.0
