On Wed 21-09-16 12:19:53, zijun_hu wrote: > From: zijun_hu <zijun_hu@xxxxxxx> > > endless loop maybe happen if either of parameter addr and end is not > page aligned for kernel API function ioremap_page_range() Does this happen in practise or this you found it by reading the code? > in order to fix this issue and alert improper range parameters to user > WARN_ON() checkup and rounding down range lower boundary are performed > firstly, loop end condition within ioremap_pte_range() is optimized due > to lack of relevant macro pte_addr_end() > > Signed-off-by: zijun_hu <zijun_hu@xxxxxxx> > --- > lib/ioremap.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/lib/ioremap.c b/lib/ioremap.c > index 86c8911..911bdca 100644 > --- a/lib/ioremap.c > +++ b/lib/ioremap.c > @@ -64,7 +64,7 @@ static int ioremap_pte_range(pmd_t *pmd, unsigned long addr, > BUG_ON(!pte_none(*pte)); > set_pte_at(&init_mm, addr, pte, pfn_pte(pfn, prot)); > pfn++; > - } while (pte++, addr += PAGE_SIZE, addr != end); > + } while (pte++, addr += PAGE_SIZE, addr < end && addr >= PAGE_SIZE); > return 0; > } Ble, this just overcomplicate things. Can we just make sure that the proper alignment is done in ioremap_page_range which is the only caller of this (and add VM_BUG_ON in ioremap_pud_range to make sure no new caller will forget about that). > > @@ -129,7 +129,9 @@ int ioremap_page_range(unsigned long addr, > int err; > > BUG_ON(addr >= end); > + WARN_ON(!PAGE_ALIGNED(addr) || !PAGE_ALIGNED(end)); maybe WARN_ON_ONCE would be sufficient to prevent from swamping logs if something just happens to do this too often in some pathological path. > > + addr = round_down(addr, PAGE_SIZE); end = round_up(end, PAGE_SIZE); wouldn't work? > start = addr; > phys_addr -= addr; > pgd = pgd_offset_k(addr); > -- > 1.9.1 > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@xxxxxxxxx. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a> -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>