[hurd] 02/06: libpager, libstore: Fix crash on ENOSPC while writing data

[Samuel Thibault]

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sthibault pushed a commit to branch upstream
in repository hurd.

commit 62953f120bcdc976a3dfb96505066228464a78dd
Author: Samuel Thibault <address@hidden>
Date:   Sun Nov 20 16:22:29 2016 +0100

    libpager, libstore: Fix crash on ENOSPC while writing data
    
    We need to save blocked signals, otherwise longjmp will not unblock
    SIGSEGV/SIGBUS, and thus next exception will kill us. Also, we need to
    make sure that the preemptor is set at the right window in main memory
    before letting a handler see it.
    
    * libpager/pager-memcpy.c (do_memcpy): Call __sync_synchronize()
    between aligning the fault preemptor and actually accessing data.
    (fault): Use siglongjmp instead of longjmp.
    (pager_memcpy): Use sigsetjmp instead of setjmp.
    * libstore/memobj.c (copy, fault, memobj_memcpy): Likewise.
---
 libpager/pager-memcpy.c | 5 +++--
 libstore/memobj.c       | 5 +++--
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/libpager/pager-memcpy.c b/libpager/pager-memcpy.c
index 7bdc248..c7a420b 100644
--- a/libpager/pager-memcpy.c
+++ b/libpager/pager-memcpy.c
@@ -121,6 +121,7 @@ pager_memcpy (struct pager *pager, memory_object_t memobj,
              /* Realign the fault preemptor for the new mapping window.  */
              preemptor->first = window;
              preemptor->last = window + window_size;
+             __sync_synchronize();
 
              if (prot == VM_PROT_READ)
                memcpy (other, (const void *) window + pageoff, copy_count);
@@ -176,7 +177,7 @@ pager_memcpy (struct pager *pager, memory_object_t memobj,
       err = pager_get_error (pager, sigcode - window + offset);
       n -= sigcode - window;
       vm_deallocate (mach_task_self (), window, window_size);
-      longjmp (buf, 1);
+      siglongjmp (buf, 1);
     }
 
   if (n == 0)
@@ -206,7 +207,7 @@ pager_memcpy (struct pager *pager, memory_object_t memobj,
   window = 0;
   window_size = 0;
 
-  if (setjmp (buf) == 0)
+  if (sigsetjmp (buf) == 0)
     hurd_catch_signal (sigmask (SIGSEGV) | sigmask (SIGBUS),
                       window, window + window_size,
                       &do_copy, (sighandler_t) &fault);
diff --git a/libstore/memobj.c b/libstore/memobj.c
index cc6c7ca..8bbc833 100644
--- a/libstore/memobj.c
+++ b/libstore/memobj.c
@@ -83,6 +83,7 @@ memobj_memcpy (memory_object_t memobj,
          /* Realign the fault preemptor for the new mapping window.  */
          preemptor->first = window;
          preemptor->last = window + windowsize;
+         __sync_synchronize();
 
          if (prot == VM_PROT_READ)
            memcpy (other, (const void *) window + pageoff,
@@ -103,7 +104,7 @@ memobj_memcpy (memory_object_t memobj,
       assert (scp->sc_error == EKERN_MEMORY_ERROR);
       err = EIO;
       to_copy -= sigcode - window;
-      longjmp (buf, 1);
+      siglongjmp (buf, 1);
     }
 
   if (to_copy == 0)
@@ -111,7 +112,7 @@ memobj_memcpy (memory_object_t memobj,
        ERR would not be initialized by the copy loop in this case.  */
     return 0;
 
-  if (setjmp (buf) == 0)
+  if (sigsetjmp (buf) == 0)
     hurd_catch_signal (sigmask (SIGSEGV) | sigmask (SIGBUS),
                       window, window + windowsize,
                       &copy, (sighandler_t) &fault);

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