io_uring/parisc: Adjust pgoff in io_uring mmap() for parisc

commit 56675f8 upstream.

The changes from commit 32832a4 ("io_uring: Fix io_uring mmap() by
using architecture-provided get_unmapped_area()") to the parisc
implementation of get_unmapped_area() broke glibc's locale-gen
executable when running on parisc.

This patch reverts those architecture-specific changes, and instead
adjusts in io_uring_mmu_get_unmapped_area() the pgoff offset which is
then given to parisc's get_unmapped_area() function.  This is much
cleaner than the previous approach, and we still will get a coherent
addresss.

This patch has no effect on other architectures (SHM_COLOUR is only
defined on parisc), and the liburing testcase stil passes on parisc.

Cc: stable@vger.kernel.org # 6.4
Signed-off-by: Helge Deller <deller@gmx.de>
Reported-by: Christoph Biedl <linux-kernel.bfrz@manchmal.in-ulm.de>
Fixes: 32832a4 ("io_uring: Fix io_uring mmap() by using architecture-provided get_unmapped_area()")
Fixes: d808459 ("io_uring: Adjust mapping wrt architecture aliasing requirements")
Link: https://lore.kernel.org/r/ZNEyGV0jyI8kOOfz@p100
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/parisc/kernel/sys_parisc.c

@@ -26,17 +26,12 @@
 #include <linux/compat.h>
 
 /*
- * Construct an artificial page offset for the mapping based on the virtual
+ * Construct an artificial page offset for the mapping based on the physical
  * address of the kernel file mapping variable.
- * If filp is zero the calculated pgoff value aliases the memory of the given
- * address. This is useful for io_uring where the mapping shall alias a kernel
- * address and a userspace adress where both the kernel and the userspace
- * access the same memory region.
  */
-#define GET_FILP_PGOFF(filp, addr)		\
-	((filp ? (((unsigned long) filp->f_mapping) >> 8)	\
-		 & ((SHM_COLOUR-1) >> PAGE_SHIFT) : 0UL)	\
-	  + (addr >> PAGE_SHIFT))
+#define GET_FILP_PGOFF(filp)		\
+	(filp ? (((unsigned long) filp->f_mapping) >> 8)	\
+		 & ((SHM_COLOUR-1) >> PAGE_SHIFT) : 0UL)
 
 static unsigned long shared_align_offset(unsigned long filp_pgoff,
 					 unsigned long pgoff)
@@ -116,7 +111,7 @@ static unsigned long arch_get_unmapped_area_common(struct file *filp,
 	do_color_align = 0;
 	if (filp || (flags & MAP_SHARED))
 		do_color_align = 1;
-	filp_pgoff = GET_FILP_PGOFF(filp, addr);
+	filp_pgoff = GET_FILP_PGOFF(filp);
 
 	if (flags & MAP_FIXED) {
 		/* Even MAP_FIXED mappings must reside within TASK_SIZE */

io_uring/io_uring.c

@@ -3466,6 +3466,8 @@ static unsigned long io_uring_mmu_get_unmapped_area(struct file *filp,
 	 * - use the kernel virtual address of the shared io_uring context
 	 *   (instead of the userspace-provided address, which has to be 0UL
 	 *   anyway).
+	 * - use the same pgoff which the get_unmapped_area() uses to
+	 *   calculate the page colouring.
 	 * For architectures without such aliasing requirements, the
 	 * architecture will return any suitable mapping because addr is 0.
 	 */
@@ -3474,6 +3476,7 @@ static unsigned long io_uring_mmu_get_unmapped_area(struct file *filp,
 	pgoff = 0;	/* has been translated to ptr above */
 #ifdef SHM_COLOUR
 	addr = (uintptr_t) ptr;
+	pgoff = addr >> PAGE_SHIFT;
 #else
 	addr = 0UL;
 #endif