[PATCH 1/3] misc: xilinx-sdfec: improve get_user_pages_fast() error handling

[John Hubbard]

This fixes the case of get_user_pages_fast() returning a -errno.
The result needs to be stored in a signed integer. And for safe
signed/unsigned comparisons, it's best to keep everything signed.
And get_user_pages_fast() also expects a signed value for number
of pages to pin.

Therefore, change most relevant variables, from u32 to int. Leave
"n" unsigned, for convenience in checking for overflow. And provide
a WARN_ON_ONCE() and early return, if overflow occurs.

Also, as long as we're tidying up: rename the page array from page,
to pages, in order to match the conventions used in most other call
sites.

Fixes: 20ec628e8007e ("misc: xilinx_sdfec: Add ability to configure LDPC")
Cc: Derek Kiernan <derek.kier...@xilinx.com>
Cc: Dragan Cvetic <dragan.cve...@xilinx.com>
Cc: Arnd Bergmann <a...@arndb.de>
Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org>
Cc: Michal Simek <michal.si...@xilinx.com>
Cc: linux-arm-ker...@lists.infradead.org
Signed-off-by: John Hubbard <jhubb...@nvidia.com>
---
 drivers/misc/xilinx_sdfec.c | 27 +++++++++++++++++----------
 1 file changed, 17 insertions(+), 10 deletions(-)

diff --git a/drivers/misc/xilinx_sdfec.c b/drivers/misc/xilinx_sdfec.c
index 71bbaa56bdb5..e2766aad9e14 100644
--- a/drivers/misc/xilinx_sdfec.c
+++ b/drivers/misc/xilinx_sdfec.c
@@ -602,10 +602,10 @@ static int xsdfec_table_write(struct xsdfec_dev *xsdfec, 
u32 offset,
                              const u32 depth)
 {
        u32 reg = 0;
-       u32 res;
-       u32 n, i;
+       int res, i, nr_pages;
+       u32 n;
        u32 *addr = NULL;
-       struct page *page[MAX_NUM_PAGES];
+       struct page *pages[MAX_NUM_PAGES];
 
        /*
         * Writes that go beyond the length of
@@ -622,15 +622,22 @@ static int xsdfec_table_write(struct xsdfec_dev *xsdfec, 
u32 offset,
        if ((len * XSDFEC_REG_WIDTH_JUMP) % PAGE_SIZE)
                n += 1;
 
-       res = get_user_pages_fast((unsigned long)src_ptr, n, 0, page);
-       if (res < n) {
-               for (i = 0; i < res; i++)
-                       put_page(page[i]);
+       if (WARN_ON_ONCE(n > INT_MAX))
+               return -EINVAL;
+
+       nr_pages = n;
+
+       res = get_user_pages_fast((unsigned long)src_ptr, nr_pages, 0, pages);
+       if (res < nr_pages) {
+               if (res > 0) {
+                       for (i = 0; i < res; i++)
+                               put_page(pages[i]);
+               }
                return -EINVAL;
        }
 
-       for (i = 0; i < n; i++) {
-               addr = kmap(page[i]);
+       for (i = 0; i < nr_pages; i++) {
+               addr = kmap(pages[i]);
                do {
                        xsdfec_regwrite(xsdfec,
                                        base_addr + ((offset + reg) *
@@ -639,7 +646,7 @@ static int xsdfec_table_write(struct xsdfec_dev *xsdfec, 
u32 offset,
                        reg++;
                } while ((reg < len) &&
                         ((reg * XSDFEC_REG_WIDTH_JUMP) % PAGE_SIZE));
-               put_page(page[i]);
+               put_page(pages[i]);
        }
        return reg;
 }
-- 
2.26.2