userfaultfd: clear flag if remap event not enabled
Subsystems (2)
PATCH v2 1/1 userfaultfd: clear flag if remap event not enabled
When the process being tracked do mremap() without UFFD_FEATURE_EVENT_REMAP on the corresponding tracking uffd file handle, we should not generate the remap event, and at the same time we should clear all the uffd flags on the new VMA. Without this patch, we can still have the VM_UFFD_MISSING|VM_UFFD_WP flags on the new VMA even the fault handling process does not even know the existance of the VMA.
CC Andrea Arcangeli <[email protected]>
CC Andrew Morton <[email protected]>
CC Mike Rapoport <[email protected]>
CC Kirill A. Shutemov <[email protected]>
CC Hugh Dickins <[email protected]>
CC Pavel Emelyanov <[email protected]>
CC Pravin Shedge <[email protected]>
Acked-by Mike Rapoport <[email protected]>
Reviewed-by Andrea Arcangeli <[email protected]>
Signed-off-by Peter Xu <[email protected]>
--- fs/userfaultfd.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)
fs/userfaultfd.c +9 -1
@@ -736,10 +736,18 @@ void mremap_userfaultfd_prep(struct vm_area_struct *vma,struct userfaultfd_ctx *ctx; ctx = vma->vm_userfaultfd_ctx.ctx; -if (ctx && (ctx->features &UFFD_FEATURE_EVENT_REMAP )) { + +if (!ctx) +return ; + +if (ctx->features &UFFD_FEATURE_EVENT_REMAP ) { vm_ctx->ctx = ctx;userfaultfd_ctx_get (ctx);WRITE_ONCE (ctx->mmap_changing, true); + }else { +/* Drop uffd context if remap feature not enabled */ + vma->vm_userfaultfd_ctx =NULL_VM_UFFD_CTX ; + vma->vm_flags &= ~(VM_UFFD_WP |VM_UFFD_MISSING ); } }
Signature · 1 line
2.17.1
Quoted 35 lines · Peter Xu
---
fs/userfaultfd.c| 10 +++++++++-1 file changed, 9 insertions(+), 1 deletion(-)fs/userfaultfd.c +9
-1@@ -736,10 +736,18 @@ void mremap_userfaultfd_prep(struct vm_area_struct *vma,struct userfaultfd_ctx *ctx; ctx = vma->vm_userfaultfd_ctx.ctx; -if (ctx && (ctx->features &UFFD_FEATURE_EVENT_REMAP )) { + +if (!ctx) +return ; + +if (ctx->features &UFFD_FEATURE_EVENT_REMAP ) { vm_ctx->ctx = ctx;userfaultfd_ctx_get (ctx);WRITE_ONCE (ctx->mmap_changing, true); + }else { +/* Drop uffd context if remap feature not enabled */ + vma->vm_userfaultfd_ctx =NULL_VM_UFFD_CTX ; + vma->vm_flags &= ~(VM_UFFD_WP |VM_UFFD_MISSING ); } }Signature · 1 line
2.17.1
Looks good.
Reviewed-by William Kucharski <[email protected]>