Messages in this thread Patch in this message | | | Date | Sun, 14 Mar 2021 23:51:14 +0300 | From | Alexey Dobriyan <> | Subject | [PATCH] prctl: fix PR_SET_MM_AUXV kernel stack leak |
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prctl(PR_SET_MM, PR_SET_MM_AUXV, addr, 1);
will copy 1 byte from userspace to (quite big) on-stack array and then stash everything to mm->saved_auxv. AT_NULL terminator will be inserted at the very end.
/proc/*/auxv handler will find that AT_NULL terminator and copy original stack contents to userspace.
This devious scheme requires CAP_SYS_RESOURCE.
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> ---
apply to >=3.5
kernel/sys.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/kernel/sys.c +++ b/kernel/sys.c @@ -2079,7 +2079,7 @@ static int prctl_set_auxv(struct mm_struct *mm, unsigned long addr, * up to the caller to provide sane values here, otherwise userspace * tools which use this vector might be unhappy. */ - unsigned long user_auxv[AT_VECTOR_SIZE]; + unsigned long user_auxv[AT_VECTOR_SIZE] = {}; if (len > sizeof(user_auxv)) return -EINVAL;
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