From b6a8b316c667f914c198a2de62e6729f359b7931 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Mon, 2 Apr 2007 14:25:31 +0200 Subject: [PATCH] [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 Acked-by: Ingo Molnar Signed-off-by: Linus Torvalds --- arch/i386/lib/usercopy.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/arch/i386/lib/usercopy.c b/arch/i386/lib/usercopy.c index d22cfc9d656c..086b3726862a 100644 --- a/arch/i386/lib/usercopy.c +++ b/arch/i386/lib/usercopy.c @@ -10,6 +10,7 @@ #include #include #include +#include #include #include @@ -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,