From: Willy Tarreau w@1wt.eu
commit 4f134b89a24b965991e7c345b9a4591821f7c2a6 upstream.
Lilith >_> and Claudio Bozzato of Cisco Talos security team reported that collect_syscall() improperly casts the syscall registers to 64-bit values leaking the uninitialized last 24 bytes on 32-bit platforms, that are visible in /proc/self/syscall.
The cause is that info->data.args are u64 while syscall_get_arguments() uses longs, as hinted by the bogus pointer cast in the function.
Let's just proceed like the other call places, by retrieving the registers into an array of longs before assigning them to the caller's array. This was successfully tested on x86_64, i386 and ppc32.
Reference: CVE-2020-28588, TALOS-2020-1211 Fixes: 631b7abacd02 ("ptrace: Remove maxargs from task_current_syscall()") Cc: Greg KH greg@kroah.com Reviewed-by: Kees Cook keescook@chromium.org Tested-by: Michael Ellerman mpe@ellerman.id.au (ppc32) Signed-off-by: Willy Tarreau w@1wt.eu Reviewed-by: Thomas Gleixner tglx@linutronix.de Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- lib/syscall.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)
--- a/lib/syscall.c +++ b/lib/syscall.c @@ -7,6 +7,7 @@
static int collect_syscall(struct task_struct *target, struct syscall_info *info) { + unsigned long args[6] = { }; struct pt_regs *regs;
if (!try_get_task_stack(target)) { @@ -27,8 +28,14 @@ static int collect_syscall(struct task_s
info->data.nr = syscall_get_nr(target, regs); if (info->data.nr != -1L) - syscall_get_arguments(target, regs, - (unsigned long *)&info->data.args[0]); + syscall_get_arguments(target, regs, args); + + info->data.args[0] = args[0]; + info->data.args[1] = args[1]; + info->data.args[2] = args[2]; + info->data.args[3] = args[3]; + info->data.args[4] = args[4]; + info->data.args[5] = args[5];
put_task_stack(target); return 0;