Messages in this thread Patch in this message | | | Date | Thu, 19 Nov 2015 16:10:43 -0800 | From | Kees Cook <> | Subject | [PATCH] fs: clear file set[ug]id when writing via mmap |
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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 <keescook@chromium.org> Cc: stable@vger.kernel.org --- 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
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