5.15-stable review patch. If anyone has any objections, please let me know.
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From: Baoquan He bhe@redhat.com
commit 8c03ebd7cdc06bd0d2fecb4d1a609ef1dbb7d0aa upstream.
Not like fault_in_readable() or fault_in_writeable(), in fault_in_safe_writeable() local variable 'start' is increased page by page to loop till the whole address range is handled. However, it mistakenly calculates the size of the handled range with 'uaddr - start'.
Fix it here.
Andreas said:
: In gfs2, fault_in_iov_iter_writeable() is used in : gfs2_file_direct_read() and gfs2_file_read_iter(), so this potentially : affects buffered as well as direct reads. This bug could cause those : gfs2 functions to spin in a loop.
Link: https://lkml.kernel.org/r/20250410035717.473207-1-bhe@redhat.com Link: https://lkml.kernel.org/r/20250410035717.473207-2-bhe@redhat.com Signed-off-by: Baoquan He bhe@redhat.com Fixes: fe673d3f5bf1 ("mm: gup: make fault_in_safe_writeable() use fixup_user_fault()") Reviewed-by: Oscar Salvador osalvador@suse.de Acked-by: David Hildenbrand david@redhat.com Cc: Andreas Gruenbacher agruenba@redhat.com Cc: Yanjun.Zhu yanjun.zhu@linux.dev Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/gup.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/mm/gup.c +++ b/mm/gup.c @@ -1768,8 +1768,8 @@ size_t fault_in_safe_writeable(const cha } while (start != end); mmap_read_unlock(mm);
- if (size > (unsigned long)uaddr - start) - return size - ((unsigned long)uaddr - start); + if (size > start - (unsigned long)uaddr) + return size - (start - (unsigned long)uaddr); return 0; } EXPORT_SYMBOL(fault_in_safe_writeable);