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authorThomas Gleixner <tglx@linutronix.de>2007-04-13 20:45:17 +0200
committerAdrian Bunk <bunk@stusta.de>2007-04-13 22:58:22 +0200
commit0243ef462fbe940dafde1f47d3ea29dbf5146b21 (patch)
tree44cf4ad4bf8680f325c1c1f096d49f45aff962d3
parent1ee709383b60148263f139af790c8b5a22c2e586 (diff)
downloadlwn-0243ef462fbe940dafde1f47d3ea29dbf5146b21.tar.gz
lwn-0243ef462fbe940dafde1f47d3ea29dbf5146b21.zip
i386: fix file_read_actor() and pipe_read() for original i386 systems
The __copy_to_user_inatomic() calls in file_read_actor() and pipe_read() are broken on original i386 machines, where WP-works-ok == false, as __copy_to_user_inatomic() on such systems calls functions which might sleep and/or contain cond_resched() calls inside of a kmap_atomic() region. The original check for WP-works-ok was in access_ok(), but got moved during the 2.5 series to fix a race vs. swap. Return the number of bytes to copy in the case where we are in an atomic region, so the non atomic code pathes in file_read_actor() and pipe_read() are taken. This could be optimized to avoid the kmap_atomicby moving the check for WP-works-ok into fault_in_pages_writeable(), but this is more intrusive and can be done later. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Adrian Bunk <bunk@stusta.de>
-rw-r--r--arch/i386/lib/usercopy.c9
1 files changed, 9 insertions, 0 deletions
diff --git a/arch/i386/lib/usercopy.c b/arch/i386/lib/usercopy.c
index 4cf981d70f45..20910daa53af 100644
--- a/arch/i386/lib/usercopy.c
+++ b/arch/i386/lib/usercopy.c
@@ -10,6 +10,7 @@
#include <linux/highmem.h>
#include <linux/blkdev.h>
#include <linux/module.h>
+#include <linux/interrupt.h>
#include <asm/uaccess.h>
#include <asm/mmx.h>
@@ -522,6 +523,14 @@ unsigned long __copy_to_user_ll(void __user *to, const void *from, unsigned long
#ifndef CONFIG_X86_WP_WORKS_OK
if (unlikely(boot_cpu_data.wp_works_ok == 0) &&
((unsigned long )to) < TASK_SIZE) {
+ /*
+ * When we are in an atomic section (see
+ * mm/filemap.c:file_read_actor), return the full
+ * length to take the slow path.
+ */
+ if (in_atomic())
+ return n;
+
/*
* CPU does not honor the WP bit when writing
* from supervisory mode, and due to preemption or SMP,