CVE-2024-39487

In the Linux kernel, the following vulnerability has been resolved:

bonding: Fix out-of-bounds read in bondoptionarpiptargets_set()

In function bondoptionarpiptargets_set(), if newval->string is an empty string, newval->string+1 will point to the byte after the string, causing an out-of-bound read.

BUG: KASAN: slab-out-of-bounds in strlen+0x7d/0xa0 lib/string.c:418 Read of size 1 at addr ffff8881119c4781 by task syz-executor665/8107 CPU: 1 PID: 8107 Comm: syz-executor665 Not tainted 6.7.0-rc7 #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 Call Trace: <TASK> _dumpstack lib/dumpstack.c:88 [inline] dumpstacklvl+0xd9/0x150 lib/dumpstack.c:106 printaddressdescription mm/kasan/report.c:364 [inline] printreport+0xc1/0x5e0 mm/kasan/report.c:475 kasanreport+0xbe/0xf0 mm/kasan/report.c:588 strlen+0x7d/0xa0 lib/string.c:418 _fortifystrlen include/linux/fortify-string.h:210 [inline] in4pton+0xa3/0x3f0 net/core/utils.c:130 bondoptionarpiptargetsset+0xc2/0x910 drivers/net/bonding/bondoptions.c:1201 _bondoptset+0x2a4/0x1030 drivers/net/bonding/bondoptions.c:767 _bondoptsetnotify+0x48/0x150 drivers/net/bonding/bondoptions.c:792 bondopttrysetrtnl+0xda/0x160 drivers/net/bonding/bondoptions.c:817 bondingsysfsstoreoption+0xa1/0x120 drivers/net/bonding/bondsysfs.c:156 devattrstore+0x54/0x80 drivers/base/core.c:2366 sysfskfwrite+0x114/0x170 fs/sysfs/file.c:136 kernfsfopwriteiter+0x337/0x500 fs/kernfs/file.c:334 callwriteiter include/linux/fs.h:2020 [inline] newsyncwrite fs/readwrite.c:491 [inline] vfswrite+0x96a/0xd80 fs/readwrite.c:584 ksyswrite+0x122/0x250 fs/readwrite.c:637 dosyscallx64 arch/x86/entry/common.c:52 [inline] dosyscall64+0x40/0x110 arch/x86/entry/common.c:83 entrySYSCALL64afterhwframe+0x63/0x6b ---[ end trace ]---

Fix it by adding a check of string length before using it.