Re: [PATCH v17 07/15] fs, arm64: untag user pointers in copy_mount_options
From: Vincenzo Frascino <vincenzo.frascino@arm.com>
Date: 2019-06-12 14:35:35
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On 12/06/2019 12:43, Andrey Konovalov wrote:
This patch is a part of a series that extends arm64 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. Reviewed-by: Kees Cook <redacted> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Andrey Konovalov <redacted>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
quoted hunk ↗ jump to hunk
--- fs/namespace.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)diff --git a/fs/namespace.c b/fs/namespace.c index b26778bdc236..2e85712a19ed 100644 --- a/fs/namespace.c +++ b/fs/namespace.c@@ -2993,7 +2993,7 @@ 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;
-- Regards, Vincenzo _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel