6.6-stable review patch. If anyone has any objections, please let me know.
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From: Jann Horn jannh@google.com
[ Upstream commit 57e2428f8df8263275344566e02c277648a4b7f1 ]
PUSH_REGS with save_ret=1 is used by interrupt entry helper functions that initially start with a UNWIND_HINT_FUNC ORC state.
However, save_ret=1 means that we clobber the helper function's return address (and then later restore the return address further down on the stack); after that point, the only thing on the stack we can unwind through is the IRET frame, so use UNWIND_HINT_IRET_REGS until we have a full pt_regs frame.
( An alternate approach would be to move the pt_regs->di overwrite down such that it is the final step of pt_regs setup; but I don't want to rearrange entry code just to make unwinding a tiny bit more elegant. )
Fixes: 9e809d15d6b6 ("x86/entry: Reduce the code footprint of the 'idtentry' macro") Signed-off-by: Jann Horn jannh@google.com Signed-off-by: Ingo Molnar mingo@kernel.org Cc: Andy Lutomirski luto@kernel.org Cc: Brian Gerst brgerst@gmail.com Cc: Juergen Gross jgross@suse.com Cc: H. Peter Anvin hpa@zytor.com Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Kees Cook keescook@chromium.org Cc: Peter Zijlstra peterz@infradead.org Cc: Josh Poimboeuf jpoimboe@redhat.com Link: https://lore.kernel.org/r/20250325-2025-03-unwind-fixes-v1-1-acd774364768@go... Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/entry/calling.h | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h index f6907627172ba..01e9593e2bd95 100644 --- a/arch/x86/entry/calling.h +++ b/arch/x86/entry/calling.h @@ -70,6 +70,8 @@ For 32-bit we have the following conventions - kernel is built with pushq %rsi /* pt_regs->si */ movq 8(%rsp), %rsi /* temporarily store the return address in %rsi */ movq %rdi, 8(%rsp) /* pt_regs->di (overwriting original return address) */ + /* We just clobbered the return address - use the IRET frame for unwinding: */ + UNWIND_HINT_IRET_REGS offset=3*8 .else pushq %rdi /* pt_regs->di */ pushq %rsi /* pt_regs->si */