Date: Tue, 21 Jun 2011 22:09:50 +0200 From: Clemens Ladisch <clemens@xxxxxxxxxx> Commit db64fe02258f (mm: rewrite vmap layer) introduced code that does address calculations under the assumption that VMAP_BLOCK_SIZE is a power of two. However, this might not be true if CONFIG_NR_CPUS is not set to a power of two. Wrong vmap_block index/offset values could lead to memory corruption. However, this has never been observed in practice (or never been diagnosed correctly); what caught this was the BUG_ON in vb_alloc() that checks for inconsistent vmap_block indices. To fix this, ensure that VMAP_BLOCK_SIZE always is a power of two. BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=31572 Reported-by: Pavel Kysilka <goldenfish@xxxxxxxxxxxx> Reported-by: Matias A. Fonzo <selk@xxxxxxxxxxx> Signed-off-by: Clemens Ladisch <clemens@xxxxxxxxxx> Signed-off-by: Stefan Richter <stefanr@xxxxxxxxxxxxxxxxx> Cc: 2.6.28+ <stable@xxxxxxxxxx> --- This fixes instant and fully repeatable crashes if NR_CPUS is not a power of two and vm_map_ram() or something like that is executed, for example firewire-ohci probe in its 2.6.38+ incarnation. mm/vmalloc.c | 7 ++++--- 1 files changed, 4 insertions(+), 3 deletions(-) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 1d34d75..d3d451b 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -732,9 +732,10 @@ static void free_unmap_vmap_area_addr(unsigned long addr) #define VMAP_BBMAP_BITS_MIN (VMAP_MAX_ALLOC*2) #define VMAP_MIN(x, y) ((x) < (y) ? (x) : (y)) /* can't use min() */ #define VMAP_MAX(x, y) ((x) > (y) ? (x) : (y)) /* can't use max() */ -#define VMAP_BBMAP_BITS VMAP_MIN(VMAP_BBMAP_BITS_MAX, \ - VMAP_MAX(VMAP_BBMAP_BITS_MIN, \ - VMALLOC_PAGES / NR_CPUS / 16)) +#define VMAP_BBMAP_BITS \ + VMAP_MIN(VMAP_BBMAP_BITS_MAX, \ + VMAP_MAX(VMAP_BBMAP_BITS_MIN, \ + VMALLOC_PAGES / roundup_pow_of_two(NR_CPUS) / 16)) #define VMAP_BLOCK_SIZE (VMAP_BBMAP_BITS * PAGE_SIZE) -- 1.7.3.2 -- Stefan Richter -=====-==-== =--- -===- http://arcgraph.de/sr/ -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>