diff options
| author | Ard Biesheuvel <ardb@kernel.org> | 2023-05-08 13:40:19 +0100 |
|---|---|---|
| committer | Russell King (Oracle) <rmk+kernel@armlinux.org.uk> | 2023-05-10 10:50:25 +0100 |
| commit | 2b951b0efbaa6c805854b60c11f08811054d50cd (patch) | |
| tree | e24b752a3498179b8502425144a2797c918adffe /arch/arm/vfp/vfphw.S | |
| parent | 46dd6078dbc7e363a8bb01209da67015a1538929 (diff) | |
ARM: 9297/1: vfp: avoid unbalanced stack on 'success' return path
Commit c76c6c4ecbec0deb5 ("ARM: 9294/2: vfp: Fix broken softirq handling
with instrumentation enabled") updated the VFP exception entry logic to
go via a C function, so that we get the compiler's version of
local_bh_disable(), which may be instrumented, and isn't generally
callable from assembler.
However, this assumes that passing an alternative 'success' return
address works in C as it does in asm, and this is only the case if the C
calls in question are tail calls, as otherwise, the stack will need some
unwinding as well.
I have already sent patches to the list that replace most of the asm
logic with C code, and so it is preferable to have a minimal fix that
addresses the issue and can be backported along with the commit that it
fixes to v6.3 from v6.4. Hopefully, we can land the C conversion for v6.5.
So instead of passing the 'success' return address as a function
argument, pass the stack address from where to pop it so that both LR
and SP have the expected value.
Fixes: c76c6c4ecbec0deb5 ("ARM: 9294/2: vfp: Fix broken softirq handling with ...")
Reported-by: syzbot+d4b00edc2d0c910d4bf4@syzkaller.appspotmail.com
Tested-by: syzbot+d4b00edc2d0c910d4bf4@syzkaller.appspotmail.com
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Tested-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Diffstat (limited to 'arch/arm/vfp/vfphw.S')
| -rw-r--r-- | arch/arm/vfp/vfphw.S | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/arch/arm/vfp/vfphw.S b/arch/arm/vfp/vfphw.S index 4d8478264d82..a4610d0f3215 100644 --- a/arch/arm/vfp/vfphw.S +++ b/arch/arm/vfp/vfphw.S @@ -172,13 +172,14 @@ vfp_hw_state_valid: @ out before setting an FPEXC that @ stops us reading stuff VFPFMXR FPEXC, r1 @ Restore FPEXC last + mov sp, r3 @ we think we have handled things + pop {lr} sub r2, r2, #4 @ Retry current instruction - if Thumb str r2, [sp, #S_PC] @ mode it's two 16-bit instructions, @ else it's one 32-bit instruction, so @ always subtract 4 from the following @ instruction address. - mov lr, r3 @ we think we have handled things local_bh_enable_and_ret: adr r0, . mov r1, #SOFTIRQ_DISABLE_OFFSET @@ -209,8 +210,9 @@ skip: process_exception: DBGSTR "bounce" + mov sp, r3 @ setup for a return to the user code. + pop {lr} mov r2, sp @ nothing stacked - regdump is at TOS - mov lr, r3 @ setup for a return to the user code. @ Now call the C code to package up the bounce to the support code @ r0 holds the trigger instruction |