diff options
| -rw-r--r-- | Documentation/security/Yama.txt | 10 | ||||
| -rw-r--r-- | security/yama/yama_lsm.c | 62 |
2 files changed, 60 insertions, 12 deletions
diff --git a/Documentation/security/Yama.txt b/Documentation/security/Yama.txt index a9511f17906..e369de2d48c 100644 --- a/Documentation/security/Yama.txt +++ b/Documentation/security/Yama.txt @@ -34,7 +34,7 @@ parent to a child process (i.e. direct "gdb EXE" and "strace EXE" still work), or with CAP_SYS_PTRACE (i.e. "gdb --pid=PID", and "strace -p PID" still work as root). -For software that has defined application-specific relationships +In mode 1, software that has defined application-specific relationships between a debugging process and its inferior (crash handlers, etc), prctl(PR_SET_PTRACER, pid, ...) can be used. An inferior can declare which other process (and its descendents) are allowed to call PTRACE_ATTACH @@ -46,6 +46,8 @@ restrictions, it can call prctl(PR_SET_PTRACER, PR_SET_PTRACER_ANY, ...) so that any otherwise allowed process (even those in external pid namespaces) may attach. +These restrictions do not change how ptrace via PTRACE_TRACEME operates. + The sysctl settings are: 0 - classic ptrace permissions: a process can PTRACE_ATTACH to any other @@ -60,6 +62,12 @@ The sysctl settings are: inferior can call prctl(PR_SET_PTRACER, debugger, ...) to declare an allowed debugger PID to call PTRACE_ATTACH on the inferior. +2 - admin-only attach: only processes with CAP_SYS_PTRACE may use ptrace + with PTRACE_ATTACH. + +3 - no attach: no processes may use ptrace with PTRACE_ATTACH. Once set, + this sysctl cannot be changed to a lower value. + The original children-only logic was based on the restrictions in grsecurity. ============================================================== diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c index 573723843a0..afb04cbb697 100644 --- a/security/yama/yama_lsm.c +++ b/security/yama/yama_lsm.c @@ -18,7 +18,12 @@ #include <linux/prctl.h> #include <linux/ratelimit.h> -static int ptrace_scope = 1; +#define YAMA_SCOPE_DISABLED 0 +#define YAMA_SCOPE_RELATIONAL 1 +#define YAMA_SCOPE_CAPABILITY 2 +#define YAMA_SCOPE_NO_ATTACH 3 + +static int ptrace_scope = YAMA_SCOPE_RELATIONAL; /* describe a ptrace relationship for potential exception */ struct ptrace_relation { @@ -251,17 +256,32 @@ static int yama_ptrace_access_check(struct task_struct *child, return rc; /* require ptrace target be a child of ptracer on attach */ - if (mode == PTRACE_MODE_ATTACH && - ptrace_scope && - !task_is_descendant(current, child) && - !ptracer_exception_found(current, child) && - !capable(CAP_SYS_PTRACE)) - rc = -EPERM; + if (mode == PTRACE_MODE_ATTACH) { + switch (ptrace_scope) { + case YAMA_SCOPE_DISABLED: + /* No additional restrictions. */ + break; + case YAMA_SCOPE_RELATIONAL: + if (!task_is_descendant(current, child) && + !ptracer_exception_found(current, child) && + !capable(CAP_SYS_PTRACE)) + rc = -EPERM; + break; + case YAMA_SCOPE_CAPABILITY: + if (!capable(CAP_SYS_PTRACE)) + rc = -EPERM; + break; + case YAMA_SCOPE_NO_ATTACH: + default: + rc = -EPERM; + break; + } + } if (rc) { char name[sizeof(current->comm)]; - printk_ratelimited(KERN_NOTICE "ptrace of non-child" - " pid %d was attempted by: %s (pid %d)\n", + printk_ratelimited(KERN_NOTICE + "ptrace of pid %d was attempted by: %s (pid %d)\n", child->pid, get_task_comm(name, current), current->pid); @@ -279,8 +299,28 @@ static struct security_operations yama_ops = { }; #ifdef CONFIG_SYSCTL +static int yama_dointvec_minmax(struct ctl_table *table, int write, + void __user *buffer, size_t *lenp, loff_t *ppos) +{ + int rc; + + if (write && !capable(CAP_SYS_PTRACE)) + return -EPERM; + + rc = proc_dointvec_minmax(table, write, buffer, lenp, ppos); + if (rc) + return rc; + + /* Lock the max value if it ever gets set. */ + if (write && *(int *)table->data == *(int *)table->extra2) + table->extra1 = table->extra2; + + return rc; +} + static int zero; static int one = 1; +static int max_scope = YAMA_SCOPE_NO_ATTACH; struct ctl_path yama_sysctl_path[] = { { .procname = "kernel", }, @@ -294,9 +334,9 @@ static struct ctl_table yama_sysctl_table[] = { .data = &ptrace_scope, .maxlen = sizeof(int), .mode = 0644, - .proc_handler = proc_dointvec_minmax, + .proc_handler = yama_dointvec_minmax, .extra1 = &zero, - .extra2 = &one, + .extra2 = &max_scope, }, { } }; |