Messages in this thread | | | Date | Fri, 3 Feb 2012 08:46:56 +0100 | From | Ingo Molnar <> | Subject | Re: [patch cr 2/4] [RFC] syscalls, x86: Add __NR_kcmp syscall v7 |
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* Cyrill Gorcunov <gorcunov@openvz.org> wrote:
> +/* Comparision type */
> + * We don't expose real in-memory order of objects for security > + * reasons, still the comparision results should be suitable for > + * sorting. Thus, we obfuscate kernel pointers values (using random > + * cookies obtaned at early boot stage) and compare the production > + * instead.
> + * 0 - equal > + * 1 - less than > + * 2 - greater than > + * 3 - not equal but ordering unavailable (reserved for future)
Broken spelling in each of those comment blocks. Are these comments write-only?
> + /* > + * Tasks are looked up in caller's > + * PID namespace only. > + */
Could be a single line.
> + > + task1 = find_task_by_vpid(pid1); > + if (!task1) { > + rcu_read_unlock(); > + return -ESRCH; > + } > + > + task2 = find_task_by_vpid(pid2); > + if (!task2) { > + put_task_struct(task1); > + rcu_read_unlock(); > + return -ESRCH; > + }
This is not the standard pattern of how we do error paths ...
> + /* > + * Note for all cases but the KCMP_FILE we > + * don't take any locks in a sake of speed. > + */
Spelling.
> + get_random_bytes(&cookies[i][j], > + sizeof(cookies[i][j]));
ugly line break.
> +late_initcall(kcmp_cookie_init);
any particular reason why this needs to be a late initcall?
> --- /dev/null > +++ linux-2.6.git/tools/testing/selftests/kcmp/Makefile > @@ -0,0 +1,35 @@ > +ifeq ($(strip $(V)),) > + E = @echo > + Q = @ > +else > + E = @\# > + Q = > +endif > +export E Q > + > +uname_M := $(shell uname -m 2>/dev/null || echo not) > +ARCH ?= $(shell echo $(uname_M) | sed -e s/i.86/i386/) > +ifeq ($(ARCH),i386) > + ARCH := X86 > + CFLAGS := -DCONFIG_X86_32 > +endif > +ifeq ($(ARCH),x86_64) > + ARCH := X86 > + CFLAGS := -DCONFIG_X86_64 > +endif > + > +CFLAGS += -I../../../../arch/x86/include/generated/ > +CFLAGS += -I../../../../include/ > + > +all: > +ifeq ($(ARCH),X86) > + $(E) " CC run_test" > + $(Q) gcc $(CFLAGS) kcmp_test.c -o run_test > +else > + $(E) "Not an x86 target, can't build breakpoints selftests" > +endif > + > +clean: > + $(E) " CLEAN" > + $(Q) rm -fr ./run_test > + $(Q) rm -fr ./test-file
Needs buy-in from the kbuild guys.
> +#ifdef CONFIG_X86_64 > +#include <asm/unistd_64.h> > +#else > +#include <asm/unistd_32.h> > +#endif
Why is asm/unistd.h not good?
> +static long sys_kcmp(int pid1, int pid2, int type, int fd1, int fd2) > +{ > + return syscall(__NR_kcmp, (long)pid1, (long)pid2, > + (long)type, (long)fd1, (long)fd2); > +}
Why is a syscall that takes long arguments defined and called with int and then cast over to long again?
> + int pid2 = getpid(); > + int ret; > + > + fd2 = open("test-file", O_RDWR, 0644); > + if (fd2 < 0) { > + perror("Can't open file"); > + exit(1); > + } > + > + /* An example of output and arguments */ > + printf("pid1: %6d pid2: %6d FD: %2d FILES: %2d VM: %2d FS: %2d " > + "SIGHAND: %2d IO: %2d SYSVSEM: %2d INV: %2d\n",
Visibly stray whitespaces.
> + /* This one should return same fd */ > + ret = sys_kcmp(pid1, pid2, KCMP_FILE, fd1, fd1); > + if (ret) { > + printf("FAIL: 0 expected but %d returned\n", ret); > + ret = -1; > + } else > + printf("PASS: 0 returned as expected\n"); > + exit(ret);
this is main(), what's wrong with the standard pattern of return ret?
I don't know whether this code is correct, but the high amount of basic cleanliness problems makes me worry about that.
Thanks,
Ingo
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