Commit-ID: e96d71359e9bbea846a2111e4469a03a055dfa6f Gitweb: https://git.kernel.org/tip/e96d71359e9bbea846a2111e4469a03a055dfa6f Author: Mathieu Desnoyers <mathieu.desnoy...@efficios.com> AuthorDate: Mon, 9 Jul 2018 15:51:50 -0400 Committer: Thomas Gleixner <t...@linutronix.de> CommitDate: Tue, 10 Jul 2018 22:18:51 +0200
rseq: Use __u64 for rseq_cs fields, validate user inputs 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. Validating the value of abort_ip field to be below TASK_SIZE ensures 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 consistently deal with invalid return addresses. Validating the value of the start_ip and post_commit_offset fields prevents overflow on arithmetic performed on those values, used to check whether abort_ip is within the rseq critical section. If validation fails, the process is killed with a segmentation fault. When the signature encountered before abort_ip does not match the expected signature, return -EINVAL rather than -EPERM to be consistent with other input validation return codes from rseq_get_rseq_cs(). Signed-off-by: Mathieu Desnoyers <mathieu.desnoy...@efficios.com> Signed-off-by: Thomas Gleixner <t...@linutronix.de> Cc: linux-...@vger.kernel.org Cc: Peter Zijlstra <pet...@infradead.org> Cc: "Paul E . McKenney" <paul...@linux.vnet.ibm.com> Cc: Boqun Feng <boqun.f...@gmail.com> Cc: Andy Lutomirski <l...@amacapital.net> Cc: Dave Watson <davejwat...@fb.com> Cc: Paul Turner <p...@google.com> Cc: Andrew Morton <a...@linux-foundation.org> Cc: Russell King <li...@arm.linux.org.uk> Cc: "H . Peter Anvin" <h...@zytor.com> Cc: Andi Kleen <a...@firstfloor.org> Cc: Chris Lameter <c...@linux.com> Cc: Ben Maurer <bmau...@fb.com> Cc: Steven Rostedt <rost...@goodmis.org> Cc: Josh Triplett <j...@joshtriplett.org> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Catalin Marinas <catalin.mari...@arm.com> Cc: Will Deacon <will.dea...@arm.com> Cc: Michael Kerrisk <mtk.manpa...@gmail.com> Cc: Joel Fernandes <joe...@google.com> Cc: "Paul E. McKenney" <paul...@linux.vnet.ibm.com> Cc: "H. Peter Anvin" <h...@zytor.com> Link: https://lkml.kernel.org/r/20180709195155.7654-2-mathieu.desnoy...@efficios.com --- include/uapi/linux/rseq.h | 6 +++--- kernel/rseq.c | 14 ++++++++++---- 2 files changed, 13 insertions(+), 7 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..16b38c5342f9 100644 --- a/kernel/rseq.c +++ b/kernel/rseq.c @@ -130,14 +130,20 @@ static int rseq_get_rseq_cs(struct task_struct *t, struct rseq_cs *rseq_cs) urseq_cs = (struct rseq_cs __user *)ptr; if (copy_from_user(rseq_cs, urseq_cs, sizeof(*rseq_cs))) return -EFAULT; - if (rseq_cs->version > 0) - return -EINVAL; + if (rseq_cs->start_ip >= TASK_SIZE || + rseq_cs->start_ip + rseq_cs->post_commit_offset >= TASK_SIZE || + rseq_cs->abort_ip >= TASK_SIZE || + rseq_cs->version > 0) + return -EINVAL; + /* Check for overflow. */ + if (rseq_cs->start_ip + rseq_cs->post_commit_offset < rseq_cs->start_ip) + return -EINVAL; /* Ensure that abort_ip is not in the critical section. */ 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; @@ -146,7 +152,7 @@ static int rseq_get_rseq_cs(struct task_struct *t, struct rseq_cs *rseq_cs) printk_ratelimited(KERN_WARNING "Possible attack attempt. Unexpected rseq signature 0x%x, expecting 0x%x (pid=%d, addr=%p).\n", sig, current->rseq_sig, current->pid, usig); - return -EPERM; + return -EINVAL; } return 0; }
