ike this:

	addr = translate_usr_offset(addr)

this means that any return value of translate_usr_offset() is stored
back as compat_ulong_t type into the addr variable.

But since translate_usr_offset() returns -1 for invalid offsets, addr
can now get the value 0xffffffff which then fails the next return-value
sanity check and thus the kernel tries to access invalid memory:

	if (addr < 0)
		break;

Fix this bug by modifying translate_usr_offset() to take and return
values of type compat_ulong_t, and by returning the value
"sizeof(struct pt_regs)" as an error indicator.

Additionally change the sanity check to check for return values
for >= sizeof(struct pt_regs).

This patch survived my compile and run-tests.

Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
œ¬NMœ