Commit ed8a66b8 authored by Andrey Konovalov's avatar Andrey Konovalov Committed by Linus Torvalds
Browse files

fs/namespace: untag user pointers in copy_mount_options

This patch is a part of a series that extends kernel ABI to allow to pass
tagged user pointers (with the top byte set to something else other than
0x00) as syscall arguments.

In copy_mount_options a user address is being subtracted from TASK_SIZE.
If the address is lower than TASK_SIZE, the size is calculated to not
allow the exact_copy_from_user() call to cross TASK_SIZE boundary.
However if the address is tagged, then the size will be calculated
incorrectly.

Untag the address before subtracting.

Link: http://lkml.kernel.org/r/1de225e4a54204bfd7f25dac2635e31aa4aa1d90.1563904656.git.andreyknvl@google.com

Signed-off-by: default avatarAndrey Konovalov <andreyknvl@google.com>
Reviewed-by: default avatarKhalid Aziz <khalid.aziz@oracle.com>
Reviewed-by: Vincenzo Frascino's avatarVincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: default avatarKees Cook <keescook@chromium.org>
Reviewed-by: Catalin Marinas's avatarCatalin Marinas <catalin.marinas@arm.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Eric Auger <eric.auger@redhat.com>
Cc: Felix Kuehling <Felix.Kuehling@amd.com>
Cc: Jens Wiklander <jens.wiklander@linaro.org>
Cc: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 5d65e7a7
......@@ -3028,7 +3028,7 @@ void *copy_mount_options(const void __user * data)
* the remainder of the page.
*/
/* copy_from_user cannot cross TASK_SIZE ! */
size = TASK_SIZE - (unsigned long)data;
size = TASK_SIZE - (unsigned long)untagged_addr(data);
if (size > PAGE_SIZE)
size = PAGE_SIZE;
......
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