From 6bbc4a4144b1a69743022ac68dfaf6e7d993abb9 Mon Sep 17 00:00:00 2001 From: Andrea Arcangeli Date: Thu, 9 Mar 2017 16:16:28 -0800 Subject: userfaultfd: shmem: __do_fault requires VM_FAULT_NOPAGE __do_fault assumes vmf->page has been initialized and is valid if VM_FAULT_NOPAGE is not returned by vma->vm_ops->fault(vma, vmf). handle_userfault() in turn should return VM_FAULT_NOPAGE if it doesn't return VM_FAULT_SIGBUS or VM_FAULT_RETRY (the other two possibilities). This VM_FAULT_NOPAGE case is only invoked when signal are pending and it didn't matter for anonymous memory before. It only started to matter since shmem was introduced. hugetlbfs also takes a different path and doesn't exercise __do_fault. Link: http://lkml.kernel.org/r/20170228154201.GH5816@redhat.com Signed-off-by: Andrea Arcangeli Reported-by: Dmitry Vyukov Cc: "Kirill A. Shutemov" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/userfaultfd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'fs/userfaultfd.c') diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 973607df579d..f62199b90fd0 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -490,7 +490,7 @@ int handle_userfault(struct vm_fault *vmf, unsigned long reason) * in such case. */ down_read(&mm->mmap_sem); - ret = 0; + ret = VM_FAULT_NOPAGE; } } -- cgit v1.2.3 From dd0db88d8094a6d9d4d1fc5fcd56ab619f54ccf8 Mon Sep 17 00:00:00 2001 From: Andrea Arcangeli Date: Thu, 9 Mar 2017 16:16:49 -0800 Subject: userfaultfd: non-cooperative: rollback userfaultfd_exit Patch series "userfaultfd non-cooperative further update for 4.11 merge window". Unfortunately I noticed one relevant bug in userfaultfd_exit while doing more testing. I've been doing testing before and this was also tested by kbuild bot and exercised by the selftest, but this bug never reproduced before. I dropped userfaultfd_exit as result. I dropped it because of implementation difficulty in receiving signals in __mmput and because I think -ENOSPC as result from the background UFFDIO_COPY should be enough already. Before I decided to remove userfaultfd_exit, I noticed userfaultfd_exit wasn't exercised by the selftest and when I tried to exercise it, after moving it to a more correct place in __mmput where it would make more sense and where the vma list is stable, it resulted in the event_wait_completion in D state. So then I added the second patch to be sure even if we call userfaultfd_event_wait_completion too late during task exit(), we won't risk to generate tasks in D state. The same check exists in handle_userfault() for the same reason, except it makes a difference there, while here is just a robustness check and it's run under WARN_ON_ONCE. While looking at the userfaultfd_event_wait_completion() function I looked back at its callers too while at it and I think it's not ok to stop executing dup_fctx on the fcs list because we relay on userfaultfd_event_wait_completion to execute userfaultfd_ctx_put(fctx->orig) which is paired against userfaultfd_ctx_get(fctx->orig) in dup_userfault just before list_add(fcs). This change only takes care of fctx->orig but this area also needs further review looking for similar problems in fctx->new. The only patch that is urgent is the first because it's an use after free during a SMP race condition that affects all processes if CONFIG_USERFAULTFD=y. Very hard to reproduce though and probably impossible without SLUB poisoning enabled. This patch (of 3): I once reproduced this oops with the userfaultfd selftest, it's not easily reproducible and it requires SLUB poisoning to reproduce. general protection fault: 0000 [#1] SMP Modules linked in: CPU: 2 PID: 18421 Comm: userfaultfd Tainted: G ------------ T 3.10.0+ #15 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.10.1-0-g8891697-prebuilt.qemu-project.org 04/01/2014 task: ffff8801f83b9440 ti: ffff8801f833c000 task.ti: ffff8801f833c000 RIP: 0010:[] [] userfaultfd_exit+0x29/0xa0 RSP: 0018:ffff8801f833fe80 EFLAGS: 00010202 RAX: ffff8801f833ffd8 RBX: 6b6b6b6b6b6b6b6b RCX: ffff8801f83b9440 RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8800baf18600 RBP: ffff8801f833fee8 R08: 0000000000000000 R09: 0000000000000001 R10: 0000000000000000 R11: ffffffff8127ceb3 R12: 0000000000000000 R13: ffff8800baf186b0 R14: ffff8801f83b99f8 R15: 00007faed746c700 FS: 0000000000000000(0000) GS:ffff88023fc80000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b CR2: 00007faf0966f028 CR3: 0000000001bc6000 CR4: 00000000000006e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Call Trace: do_exit+0x297/0xd10 SyS_exit+0x17/0x20 tracesys+0xdd/0xe2 Code: 00 00 66 66 66 66 90 55 48 89 e5 41 54 53 48 83 ec 58 48 8b 1f 48 85 db 75 11 eb 73 66 0f 1f 44 00 00 48 8b 5b 10 48 85 db 74 64 <4c> 8b a3 b8 00 00 00 4d 85 e4 74 eb 41 f6 84 24 2c 01 00 00 80 RIP [] userfaultfd_exit+0x29/0xa0 RSP ---[ end trace 9fecd6dcb442846a ]--- In the debugger I located the "mm" pointer in the stack and walking mm->mmap->vm_next through the end shows the vma->vm_next list is fully consistent and it is null terminated list as expected. So this has to be an SMP race condition where userfaultfd_exit was running while the vma list was being modified by another CPU. When userfaultfd_exit() run one of the ->vm_next pointers pointed to SLAB_POISON (RBX is the vma pointer and is 0x6b6b..). The reason is that it's not running in __mmput but while there are still other threads running and it's not holding the mmap_sem (it can't as it has to wait the even to be received by the manager). So this is an use after free that was happening for all processes. One more implementation problem aside from the race condition: userfaultfd_exit has really to check a flag in mm->flags before walking the vma or it's going to slowdown the exit() path for regular tasks. One more implementation problem: at that point signals can't be delivered so it would also create a task in D state if the manager doesn't read the event. The major design issue: it overall looks superfluous as the manager can check for -ENOSPC in the background transfer: if (mmget_not_zero(ctx->mm)) { [..] } else { return -ENOSPC; } It's safer to roll it back and re-introduce it later if at all. [rppt@linux.vnet.ibm.com: documentation fixup after removal of UFFD_EVENT_EXIT] Link: http://lkml.kernel.org/r/1488345437-4364-1-git-send-email-rppt@linux.vnet.ibm.com Link: http://lkml.kernel.org/r/20170224181957.19736-2-aarcange@redhat.com Signed-off-by: Andrea Arcangeli Signed-off-by: Mike Rapoport Acked-by: Mike Rapoport Cc: "Dr. David Alan Gilbert" Cc: Mike Kravetz Cc: Pavel Emelyanov Cc: Hillf Danton Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/vm/userfaultfd.txt | 4 ---- fs/userfaultfd.c | 28 ---------------------------- include/linux/userfaultfd_k.h | 6 ------ include/uapi/linux/userfaultfd.h | 5 +---- kernel/exit.c | 1 - 5 files changed, 1 insertion(+), 43 deletions(-) (limited to 'fs/userfaultfd.c') diff --git a/Documentation/vm/userfaultfd.txt b/Documentation/vm/userfaultfd.txt index 0e5543a920e5..bb2f945f87ab 100644 --- a/Documentation/vm/userfaultfd.txt +++ b/Documentation/vm/userfaultfd.txt @@ -172,10 +172,6 @@ the same read(2) protocol as for the page fault notifications. The manager has to explicitly enable these events by setting appropriate bits in uffdio_api.features passed to UFFDIO_API ioctl: -UFFD_FEATURE_EVENT_EXIT - enable notification about exit() of the -non-cooperative process. When the monitored process exits, the uffd -manager will get UFFD_EVENT_EXIT. - UFFD_FEATURE_EVENT_FORK - enable userfaultfd hooks for fork(). When this feature is enabled, the userfaultfd context of the parent process is duplicated into the newly created process. The manager receives diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index f62199b90fd0..16d0cc600fa9 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -775,34 +775,6 @@ void userfaultfd_unmap_complete(struct mm_struct *mm, struct list_head *uf) } } -void userfaultfd_exit(struct mm_struct *mm) -{ - struct vm_area_struct *vma = mm->mmap; - - /* - * We can do the vma walk without locking because the caller - * (exit_mm) knows it now has exclusive access - */ - while (vma) { - struct userfaultfd_ctx *ctx = vma->vm_userfaultfd_ctx.ctx; - - if (ctx && (ctx->features & UFFD_FEATURE_EVENT_EXIT)) { - struct userfaultfd_wait_queue ewq; - - userfaultfd_ctx_get(ctx); - - msg_init(&ewq.msg); - ewq.msg.event = UFFD_EVENT_EXIT; - - userfaultfd_event_wait_completion(ctx, &ewq); - - ctx->features &= ~UFFD_FEATURE_EVENT_EXIT; - } - - vma = vma->vm_next; - } -} - static int userfaultfd_release(struct inode *inode, struct file *file) { struct userfaultfd_ctx *ctx = file->private_data; diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h index 0468548acebf..f2b79bf4c895 100644 --- a/include/linux/userfaultfd_k.h +++ b/include/linux/userfaultfd_k.h @@ -72,8 +72,6 @@ extern int userfaultfd_unmap_prep(struct vm_area_struct *vma, extern void userfaultfd_unmap_complete(struct mm_struct *mm, struct list_head *uf); -extern void userfaultfd_exit(struct mm_struct *mm); - #else /* CONFIG_USERFAULTFD */ /* mm helpers */ @@ -139,10 +137,6 @@ static inline void userfaultfd_unmap_complete(struct mm_struct *mm, { } -static inline void userfaultfd_exit(struct mm_struct *mm) -{ -} - #endif /* CONFIG_USERFAULTFD */ #endif /* _LINUX_USERFAULTFD_K_H */ diff --git a/include/uapi/linux/userfaultfd.h b/include/uapi/linux/userfaultfd.h index c055947c5c98..3b059530dac9 100644 --- a/include/uapi/linux/userfaultfd.h +++ b/include/uapi/linux/userfaultfd.h @@ -18,8 +18,7 @@ * means the userland is reading). */ #define UFFD_API ((__u64)0xAA) -#define UFFD_API_FEATURES (UFFD_FEATURE_EVENT_EXIT | \ - UFFD_FEATURE_EVENT_FORK | \ +#define UFFD_API_FEATURES (UFFD_FEATURE_EVENT_FORK | \ UFFD_FEATURE_EVENT_REMAP | \ UFFD_FEATURE_EVENT_REMOVE | \ UFFD_FEATURE_EVENT_UNMAP | \ @@ -113,7 +112,6 @@ struct uffd_msg { #define UFFD_EVENT_REMAP 0x14 #define UFFD_EVENT_REMOVE 0x15 #define UFFD_EVENT_UNMAP 0x16 -#define UFFD_EVENT_EXIT 0x17 /* flags for UFFD_EVENT_PAGEFAULT */ #define UFFD_PAGEFAULT_FLAG_WRITE (1<<0) /* If this was a write fault */ @@ -163,7 +161,6 @@ struct uffdio_api { #define UFFD_FEATURE_MISSING_HUGETLBFS (1<<4) #define UFFD_FEATURE_MISSING_SHMEM (1<<5) #define UFFD_FEATURE_EVENT_UNMAP (1<<6) -#define UFFD_FEATURE_EVENT_EXIT (1<<7) __u64 features; __u64 ioctls; diff --git a/kernel/exit.c b/kernel/exit.c index e126ebf2400c..516acdb0e0ec 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -554,7 +554,6 @@ static void exit_mm(void) enter_lazy_tlb(mm, current); task_unlock(current); mm_update_next_owner(mm); - userfaultfd_exit(mm); mmput(mm); if (test_thread_flag(TIF_MEMDIE)) exit_oom_victim(); -- cgit v1.2.3 From 9a69a829f9b656c2a220d65a94ecf7b5887c5da1 Mon Sep 17 00:00:00 2001 From: Andrea Arcangeli Date: Thu, 9 Mar 2017 16:16:52 -0800 Subject: userfaultfd: non-cooperative: robustness check Similar to the handle_userfault() case, also make sure to never attempt to send any event past the PF_EXITING point of no return. This is purely a robustness check. Link: http://lkml.kernel.org/r/20170224181957.19736-3-aarcange@redhat.com Signed-off-by: Andrea Arcangeli Acked-by: Mike Rapoport Cc: "Dr. David Alan Gilbert" Cc: Mike Kravetz Cc: Pavel Emelyanov Cc: Hillf Danton Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/userfaultfd.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) (limited to 'fs/userfaultfd.c') diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 16d0cc600fa9..668bbbd2e04d 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -530,8 +530,13 @@ out: static int userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx, struct userfaultfd_wait_queue *ewq) { - int ret = 0; + int ret; + + ret = -1; + if (WARN_ON_ONCE(current->flags & PF_EXITING)) + goto out; + ret = 0; ewq->ctx = ctx; init_waitqueue_entry(&ewq->wq, current); @@ -566,7 +571,7 @@ static int userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx, * ctx may go away after this if the userfault pseudo fd is * already released. */ - +out: userfaultfd_ctx_put(ctx); return ret; } -- cgit v1.2.3 From 8c9e7bb7a41f2bbd54b2caefb274fb3de239819f Mon Sep 17 00:00:00 2001 From: Andrea Arcangeli Date: Thu, 9 Mar 2017 16:16:54 -0800 Subject: userfaultfd: non-cooperative: release all ctx in dup_userfaultfd_complete Don't stop running dup_fctx() even if userfaultfd_event_wait_completion fails as it has to run userfaultfd_ctx_put on all ctx to pair against the userfaultfd_ctx_get that was run on all fctx->orig in dup_userfaultfd. Link: http://lkml.kernel.org/r/20170224181957.19736-4-aarcange@redhat.com Signed-off-by: Andrea Arcangeli Acked-by: Mike Rapoport Cc: "Dr. David Alan Gilbert" Cc: Mike Kravetz Cc: Pavel Emelyanov Cc: Hillf Danton Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/userfaultfd.c | 18 +++++------------- 1 file changed, 5 insertions(+), 13 deletions(-) (limited to 'fs/userfaultfd.c') diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 668bbbd2e04d..dd48052e086f 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -527,16 +527,12 @@ out: return ret; } -static int userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx, - struct userfaultfd_wait_queue *ewq) +static void userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx, + struct userfaultfd_wait_queue *ewq) { - int ret; - - ret = -1; if (WARN_ON_ONCE(current->flags & PF_EXITING)) goto out; - ret = 0; ewq->ctx = ctx; init_waitqueue_entry(&ewq->wq, current); @@ -552,7 +548,6 @@ static int userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx, break; if (ACCESS_ONCE(ctx->released) || fatal_signal_pending(current)) { - ret = -1; __remove_wait_queue(&ctx->event_wqh, &ewq->wq); break; } @@ -573,7 +568,6 @@ static int userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx, */ out: userfaultfd_ctx_put(ctx); - return ret; } static void userfaultfd_event_complete(struct userfaultfd_ctx *ctx, @@ -631,7 +625,7 @@ int dup_userfaultfd(struct vm_area_struct *vma, struct list_head *fcs) return 0; } -static int dup_fctx(struct userfaultfd_fork_ctx *fctx) +static void dup_fctx(struct userfaultfd_fork_ctx *fctx) { struct userfaultfd_ctx *ctx = fctx->orig; struct userfaultfd_wait_queue ewq; @@ -641,17 +635,15 @@ static int dup_fctx(struct userfaultfd_fork_ctx *fctx) ewq.msg.event = UFFD_EVENT_FORK; ewq.msg.arg.reserved.reserved1 = (unsigned long)fctx->new; - return userfaultfd_event_wait_completion(ctx, &ewq); + userfaultfd_event_wait_completion(ctx, &ewq); } void dup_userfaultfd_complete(struct list_head *fcs) { - int ret = 0; struct userfaultfd_fork_ctx *fctx, *n; list_for_each_entry_safe(fctx, n, fcs, list) { - if (!ret) - ret = dup_fctx(fctx); + dup_fctx(fctx); list_del(&fctx->list); kfree(fctx); } -- cgit v1.2.3 From 7eb76d457fd758d396bc2e65cb0ace5aae614149 Mon Sep 17 00:00:00 2001 From: Mike Rapoport Date: Thu, 9 Mar 2017 16:17:09 -0800 Subject: userfaultfd: non-cooperative: fix fork fctx->new memleak We have a memleak in the ->new ctx if the uffd of the parent is closed before the fork event is read, nothing frees the new context. Link: http://lkml.kernel.org/r/20170302173738.18994-2-aarcange@redhat.com Signed-off-by: Mike Rapoport Signed-off-by: Andrea Arcangeli Reported-by: Andrea Arcangeli Cc: "Dr. David Alan Gilbert" Cc: Mike Kravetz Cc: Pavel Emelyanov Cc: Hillf Danton Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/userfaultfd.c | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'fs/userfaultfd.c') diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index dd48052e086f..2407249998c3 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -549,6 +549,15 @@ static void userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx, if (ACCESS_ONCE(ctx->released) || fatal_signal_pending(current)) { __remove_wait_queue(&ctx->event_wqh, &ewq->wq); + if (ewq->msg.event == UFFD_EVENT_FORK) { + struct userfaultfd_ctx *new; + + new = (struct userfaultfd_ctx *) + (unsigned long) + ewq->msg.arg.reserved.reserved1; + + userfaultfd_ctx_put(new); + } break; } -- cgit v1.2.3 From 70ccb92fdd90b35bb6f9200093d4ffd6cb38156b Mon Sep 17 00:00:00 2001 From: Andrea Arcangeli Date: Thu, 9 Mar 2017 16:17:11 -0800 Subject: userfaultfd: non-cooperative: userfaultfd_remove revalidate vma in MADV_DONTNEED userfaultfd_remove() has to be execute before zapping the pagetables or UFFDIO_COPY could keep filling pages after zap_page_range returned, which would result in non zero data after a MADV_DONTNEED. However userfaultfd_remove() may have to release the mmap_sem. This was handled correctly in MADV_REMOVE, but MADV_DONTNEED accessed a potentially stale vma (the very vma passed to zap_page_range(vma, ...)). The fix consists in revalidating the vma in case userfaultfd_remove() had to release the mmap_sem. This also optimizes away an unnecessary down_read/up_read in the MADV_REMOVE case if UFFD_EVENT_FORK had to be delivered. It all remains zero runtime cost in case CONFIG_USERFAULTFD=n as userfaultfd_remove() will be defined as "true" at build time. Link: http://lkml.kernel.org/r/20170302173738.18994-3-aarcange@redhat.com Signed-off-by: Andrea Arcangeli Acked-by: Mike Rapoport Cc: "Dr. David Alan Gilbert" Cc: Mike Kravetz Cc: Pavel Emelyanov Cc: Hillf Danton Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/userfaultfd.c | 9 +++------ include/linux/userfaultfd_k.h | 7 +++---- mm/madvise.c | 44 ++++++++++++++++++++++++++++++++++++++++--- 3 files changed, 47 insertions(+), 13 deletions(-) (limited to 'fs/userfaultfd.c') diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 2407249998c3..9fd5e51ffb31 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -695,8 +695,7 @@ void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx *vm_ctx, userfaultfd_event_wait_completion(ctx, &ewq); } -void userfaultfd_remove(struct vm_area_struct *vma, - struct vm_area_struct **prev, +bool userfaultfd_remove(struct vm_area_struct *vma, unsigned long start, unsigned long end) { struct mm_struct *mm = vma->vm_mm; @@ -705,13 +704,11 @@ void userfaultfd_remove(struct vm_area_struct *vma, ctx = vma->vm_userfaultfd_ctx.ctx; if (!ctx || !(ctx->features & UFFD_FEATURE_EVENT_REMOVE)) - return; + return true; userfaultfd_ctx_get(ctx); up_read(&mm->mmap_sem); - *prev = NULL; /* We wait for ACK w/o the mmap semaphore */ - msg_init(&ewq.msg); ewq.msg.event = UFFD_EVENT_REMOVE; @@ -720,7 +717,7 @@ void userfaultfd_remove(struct vm_area_struct *vma, userfaultfd_event_wait_completion(ctx, &ewq); - down_read(&mm->mmap_sem); + return false; } static bool has_unmap_ctx(struct userfaultfd_ctx *ctx, struct list_head *unmaps, diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h index f2b79bf4c895..48a3483dccb1 100644 --- a/include/linux/userfaultfd_k.h +++ b/include/linux/userfaultfd_k.h @@ -61,8 +61,7 @@ extern void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx *, unsigned long from, unsigned long to, unsigned long len); -extern void userfaultfd_remove(struct vm_area_struct *vma, - struct vm_area_struct **prev, +extern bool userfaultfd_remove(struct vm_area_struct *vma, unsigned long start, unsigned long end); @@ -118,11 +117,11 @@ static inline void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx *ctx, { } -static inline void userfaultfd_remove(struct vm_area_struct *vma, - struct vm_area_struct **prev, +static inline bool userfaultfd_remove(struct vm_area_struct *vma, unsigned long start, unsigned long end) { + return true; } static inline int userfaultfd_unmap_prep(struct vm_area_struct *vma, diff --git a/mm/madvise.c b/mm/madvise.c index dc5927c812d3..7a2abf0127ae 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -513,7 +513,43 @@ static long madvise_dontneed(struct vm_area_struct *vma, if (!can_madv_dontneed_vma(vma)) return -EINVAL; - userfaultfd_remove(vma, prev, start, end); + if (!userfaultfd_remove(vma, start, end)) { + *prev = NULL; /* mmap_sem has been dropped, prev is stale */ + + down_read(¤t->mm->mmap_sem); + vma = find_vma(current->mm, start); + if (!vma) + return -ENOMEM; + if (start < vma->vm_start) { + /* + * This "vma" under revalidation is the one + * with the lowest vma->vm_start where start + * is also < vma->vm_end. If start < + * vma->vm_start it means an hole materialized + * in the user address space within the + * virtual range passed to MADV_DONTNEED. + */ + return -ENOMEM; + } + if (!can_madv_dontneed_vma(vma)) + return -EINVAL; + if (end > vma->vm_end) { + /* + * Don't fail if end > vma->vm_end. If the old + * vma was splitted while the mmap_sem was + * released the effect of the concurrent + * operation may not cause MADV_DONTNEED to + * have an undefined result. There may be an + * adjacent next vma that we'll walk + * next. userfaultfd_remove() will generate an + * UFFD_EVENT_REMOVE repetition on the + * end-vma->vm_end range, but the manager can + * handle a repetition fine. + */ + end = vma->vm_end; + } + VM_WARN_ON(start >= end); + } zap_page_range(vma, start, end - start); return 0; } @@ -554,8 +590,10 @@ static long madvise_remove(struct vm_area_struct *vma, * mmap_sem. */ get_file(f); - userfaultfd_remove(vma, prev, start, end); - up_read(¤t->mm->mmap_sem); + if (userfaultfd_remove(vma, start, end)) { + /* mmap_sem was not released by userfaultfd_remove() */ + up_read(¤t->mm->mmap_sem); + } error = vfs_fallocate(f, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, offset, end - start); -- cgit v1.2.3 From 2378cd6181edd94748d699448823609977283b11 Mon Sep 17 00:00:00 2001 From: David Hildenbrand Date: Thu, 9 Mar 2017 16:17:40 -0800 Subject: userfaultfd: remove wrong comment from userfaultfd_ctx_get() It's a void function, so there is no return value; Link: http://lkml.kernel.org/r/20170309150817.7510-1-david@redhat.com Signed-off-by: David Hildenbrand Cc: Andrea Arcangeli Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/userfaultfd.c | 2 -- 1 file changed, 2 deletions(-) (limited to 'fs/userfaultfd.c') diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 9fd5e51ffb31..2bb1c72380f2 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -138,8 +138,6 @@ out: * userfaultfd_ctx_get - Acquires a reference to the internal userfaultfd * context. * @ctx: [in] Pointer to the userfaultfd context. - * - * Returns: In case of success, returns not zero. */ static void userfaultfd_ctx_get(struct userfaultfd_ctx *ctx) { -- cgit v1.2.3