The patch below does not apply to the 4.14-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 951531691c4bcaa59f56a316e018bc2ff1ddf855 Mon Sep 17 00:00:00 2001
From: "Isaac J. Manjarres" isaacm@codeaurora.org Date: Tue, 13 Aug 2019 15:37:37 -0700 Subject: [PATCH] mm/usercopy: use memory range to be accessed for wraparound check
Currently, when checking to see if accessing n bytes starting at address "ptr" will cause a wraparound in the memory addresses, the check in check_bogus_address() adds an extra byte, which is incorrect, as the range of addresses that will be accessed is [ptr, ptr + (n - 1)].
This can lead to incorrectly detecting a wraparound in the memory address, when trying to read 4 KB from memory that is mapped to the the last possible page in the virtual address space, when in fact, accessing that range of memory would not cause a wraparound to occur.
Use the memory range that will actually be accessed when considering if accessing a certain amount of bytes will cause the memory address to wrap around.
Link: http://lkml.kernel.org/r/1564509253-23287-1-git-send-email-isaacm@codeaurora... Fixes: f5509cc18daa ("mm: Hardened usercopy") Signed-off-by: Prasad Sodagudi psodagud@codeaurora.org Signed-off-by: Isaac J. Manjarres isaacm@codeaurora.org Co-developed-by: Prasad Sodagudi psodagud@codeaurora.org Reviewed-by: William Kucharski william.kucharski@oracle.com Acked-by: Kees Cook keescook@chromium.org Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: Trilok Soni tsoni@codeaurora.org Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org
diff --git a/mm/usercopy.c b/mm/usercopy.c index 2a09796edef8..98e924864554 100644 --- a/mm/usercopy.c +++ b/mm/usercopy.c @@ -147,7 +147,7 @@ static inline void check_bogus_address(const unsigned long ptr, unsigned long n, bool to_user) { /* Reject if object wraps past end of memory. */ - if (ptr + n < ptr) + if (ptr + (n - 1) < ptr) usercopy_abort("wrapped address", NULL, to_user, 0, ptr + n);
/* Reject if NULL or ZERO-allocation. */