mm: drop per-VMA lock when returning VM_FAULT_RETRY or VM_FAULT_COMPLETED

handle_mm_fault returning VM_FAULT_RETRY or VM_FAULT_COMPLETED means
mmap_lock has been released.  However with per-VMA locks behavior is
different and the caller should still release it.  To make the rules
consistent for the caller, drop the per-VMA lock when returning
VM_FAULT_RETRY or VM_FAULT_COMPLETED.  Currently the only path returning
VM_FAULT_RETRY under per-VMA locks is do_swap_page and no path returns
VM_FAULT_COMPLETED for now.

[willy@infradead.org: fix riscv]
Link: https://lkml.kernel.org/r/CAJuCfpE6GWEx1rPBmNpUfoD5o-gNFz9-UFywzCE2PbEGBiVz7g@mail.gmail.com
Link: https://lkml.kernel.org/r/20230630211957.1341547-4-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Acked-by: Peter Xu <peterx@redhat.com>
Tested-by: Conor Dooley <conor.dooley@microchip.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Hillf Danton <hdanton@sina.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: Laurent Dufour <ldufour@linux.ibm.com>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Michel Lespinasse <michel@lespinasse.org>
Cc: Minchan Kim <minchan@google.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Punit Agrawal <punit.agrawal@bytedance.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 103fcbd..2e5d1e2 100644 (file)
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -599,7 +599,8 @@ static int __kprobes do_page_fault(unsigned long far, unsigned long esr,
                goto lock_mmap;
        }
        fault = handle_mm_fault(vma, addr, mm_flags | FAULT_FLAG_VMA_LOCK, regs);
-       vma_end_read(vma);
+       if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED)))
+               vma_end_read(vma);
 
        if (!(fault & VM_FAULT_RETRY)) {
                count_vm_vma_lock_event(VMA_LOCK_SUCCESS);

diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index fafce6b..b172309 100644 (file)
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -488,7 +488,8 @@ static int ___do_page_fault(struct pt_regs *regs, unsigned long address,
        }
 
        fault = handle_mm_fault(vma, address, flags | FAULT_FLAG_VMA_LOCK, regs);
-       vma_end_read(vma);
+       if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED)))
+               vma_end_read(vma);
 
        if (!(fault & VM_FAULT_RETRY)) {
                count_vm_vma_lock_event(VMA_LOCK_SUCCESS);

diff --git a/arch/riscv/mm/fault.c b/arch/riscv/mm/fault.c
index 046732f..6115d75 100644 (file)
--- a/arch/riscv/mm/fault.c
+++ b/arch/riscv/mm/fault.c
@@ -296,7 +296,8 @@ void handle_page_fault(struct pt_regs *regs)
        }
 
        fault = handle_mm_fault(vma, addr, flags | FAULT_FLAG_VMA_LOCK, regs);
-       vma_end_read(vma);
+       if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED)))
+               vma_end_read(vma);
 
        if (!(fault & VM_FAULT_RETRY)) {
                count_vm_vma_lock_event(VMA_LOCK_SUCCESS);

diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
index 6f6b988..a063774 100644 (file)
--- a/arch/s390/mm/fault.c
+++ b/arch/s390/mm/fault.c
@@ -417,7 +417,8 @@ static inline vm_fault_t do_exception(struct pt_regs *regs, int access)
                goto lock_mmap;
        }
        fault = handle_mm_fault(vma, address, flags | FAULT_FLAG_VMA_LOCK, regs);
-       vma_end_read(vma);
+       if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED)))
+               vma_end_read(vma);
        if (!(fault & VM_FAULT_RETRY)) {
                count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
                if (likely(!(fault & VM_FAULT_ERROR)))

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 787da09..2e861b9 100644 (file)
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -1340,7 +1340,8 @@ void do_user_addr_fault(struct pt_regs *regs,
                goto lock_mmap;
        }
        fault = handle_mm_fault(vma, address, flags | FAULT_FLAG_VMA_LOCK, regs);
-       vma_end_read(vma);
+       if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED)))
+               vma_end_read(vma);
 
        if (!(fault & VM_FAULT_RETRY)) {
                count_vm_vma_lock_event(VMA_LOCK_SUCCESS);

diff --git a/mm/memory.c b/mm/memory.c
index f9c3ad4..b9c3780 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3747,6 +3747,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 
        if (vmf->flags & FAULT_FLAG_VMA_LOCK) {
                ret = VM_FAULT_RETRY;
+               vma_end_read(vma);
                goto out;
        }
 
@@ -5248,6 +5249,17 @@ static vm_fault_t sanitize_fault_flags(struct vm_area_struct *vma,
                                 !is_cow_mapping(vma->vm_flags)))
                        return VM_FAULT_SIGSEGV;
        }
+#ifdef CONFIG_PER_VMA_LOCK
+       /*
+        * Per-VMA locks can't be used with FAULT_FLAG_RETRY_NOWAIT because of
+        * the assumption that lock is dropped on VM_FAULT_RETRY.
+        */
+       if (WARN_ON_ONCE((*flags &
+                       (FAULT_FLAG_VMA_LOCK | FAULT_FLAG_RETRY_NOWAIT)) ==
+                       (FAULT_FLAG_VMA_LOCK | FAULT_FLAG_RETRY_NOWAIT)))
+               return VM_FAULT_SIGSEGV;
+#endif
+
        return 0;
 }