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exec: fix set_binfmt() vs sys_delete_module() race

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sys_delete_module() can set MODULE_STATE_GOING after
search_binary_handler() does try_module_get().  In this case
set_binfmt()->try_module_get() fails but since none of the callers
check the returned error, the task will run with the wrong old
->binfmt.

The proper fix should change all ->load_binary() methods, but we can
rely on fact that the caller must hold a reference to binfmt->module
and use __module_get() which never fails.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Oleg Nesterov 2009-09-23 15:56:59 -07:00 committed by Linus Torvalds
parent 61be228a06
commit 964ee7df90
2 changed files with 6 additions and 10 deletions
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14
fs/exec.c
View file

@ -1395,18 +1395,14 @@ out_ret:
return retval;
}
int set_binfmt(struct linux_binfmt *new)
void set_binfmt(struct linux_binfmt *new)
{
struct linux_binfmt *old = current->binfmt;
if (current->binfmt)
module_put(current->binfmt->module);
if (new) {
if (!try_module_get(new->module))
return -1;
}
current->binfmt = new;
if (old)
module_put(old->module);
return 0;
if (new)
__module_get(new->module);
}
EXPORT_SYMBOL(set_binfmt);

2
include/linux/binfmts.h
View file

@ -120,7 +120,7 @@ extern int copy_strings_kernel(int argc,char ** argv,struct linux_binprm *bprm);
extern int prepare_bprm_creds(struct linux_binprm *bprm);
extern void install_exec_creds(struct linux_binprm *bprm);
extern void do_coredump(long signr, int exit_code, struct pt_regs *regs);
extern int set_binfmt(struct linux_binfmt *new);
extern void set_binfmt(struct linux_binfmt *new);
extern void free_bprm(struct linux_binprm *);
#endif /* __KERNEL__ */