Gitweb:     
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=b6a8b316c667f914c198a2de62e6729f359b7931
Commit:     b6a8b316c667f914c198a2de62e6729f359b7931
Parent:     f991519c197534811046e5e47389b6fafcdf1e48
Author:     Thomas Gleixner <[EMAIL PROTECTED]>
AuthorDate: Mon Apr 2 14:25:31 2007 +0200
Committer:  Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Mon Apr 2 10:07:25 2007 -0700

    [PATCH] 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 <[EMAIL PROTECTED]>
    Acked-by: Ingo Molnar <[EMAIL PROTECTED]>
    Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
---
 arch/i386/lib/usercopy.c |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/arch/i386/lib/usercopy.c b/arch/i386/lib/usercopy.c
index d22cfc9..086b372 100644
--- a/arch/i386/lib/usercopy.c
+++ b/arch/i386/lib/usercopy.c
@@ -10,6 +10,7 @@
 #include <linux/blkdev.h>
 #include <linux/module.h>
 #include <linux/backing-dev.h>
+#include <linux/interrupt.h>
 #include <asm/uaccess.h>
 #include <asm/mmx.h>
 
@@ -719,6 +720,14 @@ unsigned long __copy_to_user_ll(void __user *to, const 
void *from,
 #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,
-
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