Re: [PATCH] powerpc/xive/spapr: correct bitmap allocation size
From: Cédric Le Goater <clg@kaod.org>
Date: 2022-06-23 19:58:38
On 6/23/22 20:25, Nathan Lynch wrote:
kasan detects access beyond the end of the xibm->bitmap allocation: BUG: KASAN: slab-out-of-bounds in _find_first_zero_bit+0x40/0x140 Read of size 8 at addr c00000001d1d0118 by task swapper/0/1 CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.19.0-rc2-00001-g90df023b36dd #28 Call Trace: [c00000001d98f770] [c0000000012baab8] dump_stack_lvl+0xac/0x108 (unreliable) [c00000001d98f7b0] [c00000000068faac] print_report+0x37c/0x710 [c00000001d98f880] [c0000000006902c0] kasan_report+0x110/0x354 [c00000001d98f950] [c000000000692324] __asan_load8+0xa4/0xe0 [c00000001d98f970] [c0000000011c6ed0] _find_first_zero_bit+0x40/0x140 [c00000001d98f9b0] [c0000000000dbfbc] xive_spapr_get_ipi+0xcc/0x260 [c00000001d98fa70] [c0000000000d6d28] xive_setup_cpu_ipi+0x1e8/0x450 [c00000001d98fb30] [c000000004032a20] pSeries_smp_probe+0x5c/0x118 [c00000001d98fb60] [c000000004018b44] smp_prepare_cpus+0x944/0x9ac [c00000001d98fc90] [c000000004009f9c] kernel_init_freeable+0x2d4/0x640 [c00000001d98fd90] [c0000000000131e8] kernel_init+0x28/0x1d0 [c00000001d98fe10] [c00000000000cd54] ret_from_kernel_thread+0x5c/0x64 Allocated by task 0: kasan_save_stack+0x34/0x70 __kasan_kmalloc+0xb4/0xf0 __kmalloc+0x268/0x540 xive_spapr_init+0x4d0/0x77c pseries_init_irq+0x40/0x27c init_IRQ+0x44/0x84 start_kernel+0x2a4/0x538 start_here_common+0x1c/0x20 The buggy address belongs to the object at c00000001d1d0118 which belongs to the cache kmalloc-8 of size 8 The buggy address is located 0 bytes inside of 8-byte region [c00000001d1d0118, c00000001d1d0120) The buggy address belongs to the physical page: page:c00c000000074740 refcount:1 mapcount:0 mapping:0000000000000000 index:0xc00000001d1d0558 pfn:0x1d1d flags: 0x7ffff000000200(slab|node=0|zone=0|lastcpupid=0x7ffff) raw: 007ffff000000200 c00000001d0003c8 c00000001d0003c8 c00000001d010480 raw: c00000001d1d0558 0000000001e1000a 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: c00000001d1d0000: fc 00 fc fc fc fc fc fc fc fc fc fc fc fc fc fc c00000001d1d0080: fc fc 00 fc fc fc fc fc fc fc fc fc fc fc fc fcquoted
c00000001d1d0100: fc fc fc 02 fc fc fc fc fc fc fc fc fc fc fc fc^ c00000001d1d0180: fc fc fc fc 04 fc fc fc fc fc fc fc fc fc fc fc c00000001d1d0200: fc fc fc fc fc 04 fc fc fc fc fc fc fc fc fc fc This happens because the allocation uses the wrong unit (bits) when it should pass (BITS_TO_LONGS(count) * sizeof(long)) or equivalent. With small numbers of bits, the allocated object can be smaller than sizeof(long), which results in invalid accesses. Use bitmap_zalloc() to allocate and initialize the irq bitmap, paired with bitmap_free() for consistency. Signed-off-by: Nathan Lynch <redacted>
Reviewed-by: Cédric Le Goater <clg@kaod.org> Thanks, C.
quoted hunk ↗ jump to hunk
--- arch/powerpc/sysdev/xive/spapr.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)diff --git a/arch/powerpc/sysdev/xive/spapr.c b/arch/powerpc/sysdev/xive/spapr.c index 7d5128676e83..d02911e78cfc 100644 --- a/arch/powerpc/sysdev/xive/spapr.c +++ b/arch/powerpc/sysdev/xive/spapr.c@@ -15,6 +15,7 @@ #include <linux/of_fdt.h> #include <linux/slab.h> #include <linux/spinlock.h> +#include <linux/bitmap.h> #include <linux/cpumask.h> #include <linux/mm.h> #include <linux/delay.h>@@ -57,7 +58,7 @@ static int __init xive_irq_bitmap_add(int base, int count) spin_lock_init(&xibm->lock); xibm->base = base; xibm->count = count; - xibm->bitmap = kzalloc(xibm->count, GFP_KERNEL); + xibm->bitmap = bitmap_zalloc(xibm->count, GFP_KERNEL); if (!xibm->bitmap) { kfree(xibm); return -ENOMEM;@@ -75,7 +76,7 @@ static void xive_irq_bitmap_remove_all(void) list_for_each_entry_safe(xibm, tmp, &xive_irq_bitmaps, list) { list_del(&xibm->list); - kfree(xibm->bitmap); + bitmap_free(xibm->bitmap); kfree(xibm); } }