[ Upstream commit 41e71dbb0e0a0fe214545fe64af031303a08524c ]
Guenter reported dodgy crashes on an i386-nosmp build using GCC-11
that had the form of endless traps until entry stack exhaust and then
#DF from the stack guard.
It turned out that pti_clone_pgtable() had alignment assumptions on
the start address, notably it hard assumes start is PMD aligned. This
is true on x86_64, but very much not true on i386.
These assumptions can cause the end condition to malfunction, leading
to a 'short' clone. Guess what happens when the user mapping has a
short copy of the entry text?
Use the correct increment form for addr to avoid alignment
assumptions.
Fixes: 16a3fe634f6a ("x86/mm/pti: Clone kernel-image on PTE level for 32 bit")
Reported-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20240731163105.GG33588@noisy.programming.kicks-ass.net
Signed-off-by: Sasha Levin <sashal@kernel.org>
