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[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 <tglx@linutronix.de> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -10,6 +10,7 @@
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#include <linux/blkdev.h>
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#include <linux/module.h>
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#include <linux/backing-dev.h>
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#include <linux/interrupt.h>
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#include <asm/uaccess.h>
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#include <asm/mmx.h>
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@ -719,6 +720,14 @@ unsigned long __copy_to_user_ll(void __user *to, const void *from,
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#ifndef CONFIG_X86_WP_WORKS_OK
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if (unlikely(boot_cpu_data.wp_works_ok == 0) &&
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((unsigned long )to) < TASK_SIZE) {
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/*
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* When we are in an atomic section (see
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* mm/filemap.c:file_read_actor), return the full
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* length to take the slow path.
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*/
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if (in_atomic())
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return n;
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/*
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* CPU does not honor the WP bit when writing
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* from supervisory mode, and due to preemption or SMP,
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