Normally, when a user can modify a file that has setuid or setgid bits, those bits are cleared when they are not the file owner or a member of the group. This is enforced when using write() directly but not when writing to a shared mmap on the file. This could allow the file writer to gain privileges by changing the binary without losing the setuid/setgid bits.
Signed-off-by: Kees Cook <[email protected]> Cc: [email protected] --- mm/memory.c | 1 + 1 file changed, 1 insertion(+) diff --git a/mm/memory.c b/mm/memory.c index deb679c31f2a..4c970a4e0057 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2036,6 +2036,7 @@ static inline int wp_page_reuse(struct mm_struct *mm, if (!page_mkwrite) file_update_time(vma->vm_file); + file_remove_privs(vma->vm_file); } return VM_FAULT_WRITE; -- 1.9.1 -- Kees Cook Chrome OS Security -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
