We have got KASAN splat when tried to set /proc/sys/fs/file-max: BUG: KASAN: global-out-of-bounds in __do_proc_doulongvec_minmax+0x3e4/0x8f0 Read of size 8 at addr ffff20000f9b2980 by task file-max.sh/36819 Call trace: dump_backtrace+0x0/0x3f8 show_stack+0x3c/0x60 dump_stack+0x150/0x1a8 print_address_description+0x2b8/0x5a0 kasan_report+0x278/0x648 __asan_load8+0x124/0x170 __do_proc_doulongvec_minmax+0x3e4/0x8f0 proc_doulongvec_minmax+0x80/0xa0 proc_sys_call_handler+0x188/0x2a0 proc_sys_write+0x5c/0x80 __vfs_write+0x118/0x578 vfs_write+0x184/0x418 ksys_write+0xfc/0x1e8 __arm64_sys_write+0x88/0xa8 el0_svc_common+0x1a4/0x500 el0_svc_handler+0xb8/0x180 el0_svc+0x8/0xc The buggy address belongs to the variable: zero+0x0/0x40 The cause is that proc_doulongvec_minmax() is trying to cast an int pointer (namely &zero) to a unsigned long pointer, and dereferencing it. Although the warning seems does no harm, because zero will be placed in a .bss section, but it's better to kill the KASAN warning by redefining zero as a unsigned long, so it's OK whenever it is accessed as an int or a a unsigned long. An alternative fix seems to be set the minimal value of file-max to be 1, so one_ul can be used instead, but I'm not sure whether or not a file-max with a value of zero has special purpose (e.g., prohibit the file-related activities of all no-privileged users). Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx> --- kernel/sysctl.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/sysctl.c b/kernel/sysctl.c index e5da394d1ca3..03846e015013 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -124,7 +124,7 @@ static int sixty = 60; static int __maybe_unused neg_one = -1; -static int zero; +static unsigned long zero; static int __maybe_unused one = 1; static int __maybe_unused two = 2; static int __maybe_unused four = 4; -- 2.16.2.dirty
