In the Linux kernel, the following vulnerability has been resolved: powerpc/xive/spapr: correct bitmap allocation size kasan detects access beyond the end of the xibm->bitmap allocation: BUG: KASAN: slab-out-of-bounds in findfirstzerobit+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] dumpstacklvl+0xac/0x108 (unreliable) [c00000001d98f7b0] [c00000000068faac] printreport+0x37c/0x710 [c00000001d98f880] [c0000000006902c0] kasanreport+0x110/0x354 [c00000001d98f950] [c000000000692324] _asanload8+0xa4/0xe0 [c00000001d98f970] [c0000000011c6ed0] findfirstzerobit+0x40/0x140 [c00000001d98f9b0] [c0000000000dbfbc] xivespaprgetipi+0xcc/0x260 [c00000001d98fa70] [c0000000000d6d28] xivesetupcpuipi+0x1e8/0x450 [c00000001d98fb30] [c000000004032a20] pSeriessmpprobe+0x5c/0x118 [c00000001d98fb60] [c000000004018b44] smppreparecpus+0x944/0x9ac [c00000001d98fc90] [c000000004009f9c] kernelinitfreeable+0x2d4/0x640 [c00000001d98fd90] [c0000000000131e8] kernelinit+0x28/0x1d0 [c00000001d98fe10] [c00000000000cd54] retfromkernelthread+0x5c/0x64 Allocated by task 0: kasansavestack+0x34/0x70 _kasankmalloc+0xb4/0xf0 _kmalloc+0x268/0x540 xivespaprinit+0x4d0/0x77c pseriesinitirq+0x40/0x27c initIRQ+0x44/0x84 startkernel+0x2a4/0x538 startherecommon+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 fc >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 (BITSTOLONGS(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 bitmapzalloc() to allocate and initialize the irq bitmap, paired with bitmap_free() for consistency.