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![Oleg Nesterov](/assets/img/avatar_default.png)
task_struct->pesonality is "unsigned int", but sys_personality() paths use "unsigned long pesonality". This means that every assignment or comparison is not right. In particular, if this argument does not fit into "unsigned int" __set_personality() changes the caller's personality and then sys_personality() returns -EINVAL. Turn this argument into "unsigned int" and avoid overflows. Obviously, this is the user-visible change, we just ignore the upper bits. But this can't break the sane application. There is another thing which can confuse the poorly written applications. User-space thinks that this syscall returns int, not long. This means that the returned value can be negative and look like the error code. But note that libc won't be confused and thus errno won't be set, and with this patch the user-space can never get -1 unless sys_personality() really fails. And, most importantly, the negative RET != -1 is only possible if that app previously called personality(RET). Pointed-out-by: Wenming Zhang <wezhang@redhat.com> Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
207 lines
4.5 KiB
C
207 lines
4.5 KiB
C
/*
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* Handling of different ABIs (personalities).
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*
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* We group personalities into execution domains which have their
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* own handlers for kernel entry points, signal mapping, etc...
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*
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* 2001-05-06 Complete rewrite, Christoph Hellwig (hch@infradead.org)
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*/
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/kmod.h>
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#include <linux/module.h>
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#include <linux/personality.h>
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#include <linux/proc_fs.h>
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#include <linux/sched.h>
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#include <linux/seq_file.h>
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#include <linux/syscalls.h>
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#include <linux/sysctl.h>
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#include <linux/types.h>
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#include <linux/fs_struct.h>
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static void default_handler(int, struct pt_regs *);
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static struct exec_domain *exec_domains = &default_exec_domain;
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static DEFINE_RWLOCK(exec_domains_lock);
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static unsigned long ident_map[32] = {
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0, 1, 2, 3, 4, 5, 6, 7,
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8, 9, 10, 11, 12, 13, 14, 15,
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16, 17, 18, 19, 20, 21, 22, 23,
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24, 25, 26, 27, 28, 29, 30, 31
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};
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struct exec_domain default_exec_domain = {
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.name = "Linux", /* name */
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.handler = default_handler, /* lcall7 causes a seg fault. */
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.pers_low = 0, /* PER_LINUX personality. */
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.pers_high = 0, /* PER_LINUX personality. */
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.signal_map = ident_map, /* Identity map signals. */
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.signal_invmap = ident_map, /* - both ways. */
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};
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static void
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default_handler(int segment, struct pt_regs *regp)
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{
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set_personality(0);
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if (current_thread_info()->exec_domain->handler != default_handler)
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current_thread_info()->exec_domain->handler(segment, regp);
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else
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send_sig(SIGSEGV, current, 1);
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}
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static struct exec_domain *
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lookup_exec_domain(unsigned int personality)
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{
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unsigned int pers = personality(personality);
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struct exec_domain *ep;
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read_lock(&exec_domains_lock);
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for (ep = exec_domains; ep; ep = ep->next) {
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if (pers >= ep->pers_low && pers <= ep->pers_high)
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if (try_module_get(ep->module))
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goto out;
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}
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#ifdef CONFIG_MODULES
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read_unlock(&exec_domains_lock);
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request_module("personality-%d", pers);
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read_lock(&exec_domains_lock);
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for (ep = exec_domains; ep; ep = ep->next) {
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if (pers >= ep->pers_low && pers <= ep->pers_high)
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if (try_module_get(ep->module))
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goto out;
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}
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#endif
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ep = &default_exec_domain;
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out:
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read_unlock(&exec_domains_lock);
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return (ep);
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}
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int
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register_exec_domain(struct exec_domain *ep)
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{
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struct exec_domain *tmp;
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int err = -EBUSY;
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if (ep == NULL)
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return -EINVAL;
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if (ep->next != NULL)
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return -EBUSY;
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write_lock(&exec_domains_lock);
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for (tmp = exec_domains; tmp; tmp = tmp->next) {
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if (tmp == ep)
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goto out;
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}
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ep->next = exec_domains;
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exec_domains = ep;
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err = 0;
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out:
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write_unlock(&exec_domains_lock);
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return (err);
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}
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int
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unregister_exec_domain(struct exec_domain *ep)
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{
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struct exec_domain **epp;
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epp = &exec_domains;
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write_lock(&exec_domains_lock);
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for (epp = &exec_domains; *epp; epp = &(*epp)->next) {
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if (ep == *epp)
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goto unregister;
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}
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write_unlock(&exec_domains_lock);
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return -EINVAL;
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unregister:
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*epp = ep->next;
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ep->next = NULL;
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write_unlock(&exec_domains_lock);
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return 0;
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}
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int
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__set_personality(unsigned int personality)
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{
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struct exec_domain *ep, *oep;
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ep = lookup_exec_domain(personality);
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if (ep == current_thread_info()->exec_domain) {
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current->personality = personality;
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module_put(ep->module);
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return 0;
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}
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current->personality = personality;
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oep = current_thread_info()->exec_domain;
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current_thread_info()->exec_domain = ep;
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module_put(oep->module);
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return 0;
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}
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#ifdef CONFIG_PROC_FS
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static int execdomains_proc_show(struct seq_file *m, void *v)
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{
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struct exec_domain *ep;
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read_lock(&exec_domains_lock);
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for (ep = exec_domains; ep; ep = ep->next)
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seq_printf(m, "%d-%d\t%-16s\t[%s]\n",
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ep->pers_low, ep->pers_high, ep->name,
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module_name(ep->module));
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read_unlock(&exec_domains_lock);
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return 0;
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}
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static int execdomains_proc_open(struct inode *inode, struct file *file)
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{
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return single_open(file, execdomains_proc_show, NULL);
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}
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static const struct file_operations execdomains_proc_fops = {
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.open = execdomains_proc_open,
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.read = seq_read,
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.llseek = seq_lseek,
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.release = single_release,
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};
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static int __init proc_execdomains_init(void)
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{
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proc_create("execdomains", 0, NULL, &execdomains_proc_fops);
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return 0;
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}
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module_init(proc_execdomains_init);
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#endif
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SYSCALL_DEFINE1(personality, unsigned int, personality)
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{
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unsigned int old = current->personality;
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if (personality != 0xffffffff) {
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set_personality(personality);
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if (current->personality != personality)
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return -EINVAL;
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}
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return old;
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}
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EXPORT_SYMBOL(register_exec_domain);
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EXPORT_SYMBOL(unregister_exec_domain);
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EXPORT_SYMBOL(__set_personality);
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