metag/usercopy: Add early abort to copy_to_user

commit fb8ea062a8f2e85256e13f55696c5c5f0dfdcc8b upstream.

When copying to userland on Meta, if any faults are encountered
immediately abort the copy instead of continuing on and repeatedly
faulting, and worse potentially copying further bytes successfully to
subsequent valid pages.

Fixes: 373cd784d0fc ("metag: Memory handling")
Reported-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: linux-metag@vger.kernel.org
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Willy Tarreau <w@1wt.eu>

diff --git a/arch/metag/lib/usercopy.c b/arch/metag/lib/usercopy.c
index a26c8897b2a0b6bd163c3de10c987933f98f3052..212c99a1b76ee196b7f89f784d5d43bed884d00d 100644 (file)
--- a/arch/metag/lib/usercopy.c
+++ b/arch/metag/lib/usercopy.c
@@ -538,23 +538,31 @@ unsigned long __copy_user(void __user *pdst, const void *psrc,
        if ((unsigned long) src & 1) {
                __asm_copy_to_user_1(dst, src, retn);
                n--;
+               if (retn)
+                       return retn + n;
        }
        if ((unsigned long) dst & 1) {
                /* Worst case - byte copy */
                while (n > 0) {
                        __asm_copy_to_user_1(dst, src, retn);
                        n--;
+                       if (retn)
+                               return retn + n;
                }
        }
        if (((unsigned long) src & 2) && n >= 2) {
                __asm_copy_to_user_2(dst, src, retn);
                n -= 2;
+               if (retn)
+                       return retn + n;
        }
        if ((unsigned long) dst & 2) {
                /* Second worst case - word copy */
                while (n >= 2) {
                        __asm_copy_to_user_2(dst, src, retn);
                        n -= 2;
+                       if (retn)
+                               return retn + n;
                }
        }
 
@@ -569,6 +577,8 @@ unsigned long __copy_user(void __user *pdst, const void *psrc,
                while (n >= 8) {
                        __asm_copy_to_user_8x64(dst, src, retn);
                        n -= 8;
+                       if (retn)
+                               return retn + n;
                }
        }
        if (n >= RAPF_MIN_BUF_SIZE) {
@@ -581,6 +591,8 @@ unsigned long __copy_user(void __user *pdst, const void *psrc,
                while (n >= 8) {
                        __asm_copy_to_user_8x64(dst, src, retn);
                        n -= 8;
+                       if (retn)
+                               return retn + n;
                }
        }
 #endif
@@ -588,11 +600,15 @@ unsigned long __copy_user(void __user *pdst, const void *psrc,
        while (n >= 16) {
                __asm_copy_to_user_16(dst, src, retn);
                n -= 16;
+               if (retn)
+                       return retn + n;
        }
 
        while (n >= 4) {
                __asm_copy_to_user_4(dst, src, retn);
                n -= 4;
+               if (retn)
+                       return retn + n;
        }
 
        switch (n) {
@@ -609,6 +625,10 @@ unsigned long __copy_user(void __user *pdst, const void *psrc,
                break;
        }
 
+       /*
+        * If we get here, retn correctly reflects the number of failing
+        * bytes.
+        */
        return retn;
 }
 EXPORT_SYMBOL(__copy_user);