This is a note to let you know that I've just added the patch titled
x86/asm/entry/64: Remove a bogus 'ret_from_fork' optimization
to the 3.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-asm-entry-64-remove-a-bogus-ret_from_fork-optimization.patch
and it can be found in the queue-3.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 956421fbb74c3a6261903f3836c0740187cf038b Mon Sep 17 00:00:00 2001
From: Andy Lutomirski <[email protected]>
Date: Thu, 5 Mar 2015 01:09:44 +0100
Subject: x86/asm/entry/64: Remove a bogus 'ret_from_fork' optimization
From: Andy Lutomirski <[email protected]>
commit 956421fbb74c3a6261903f3836c0740187cf038b upstream.
'ret_from_fork' checks TIF_IA32 to determine whether 'pt_regs' and
the related state make sense for 'ret_from_sys_call'. This is
entirely the wrong check. TS_COMPAT would make a little more
sense, but there's really no point in keeping this optimization
at all.
This fixes a return to the wrong user CS if we came from int
0x80 in a 64-bit task.
Signed-off-by: Andy Lutomirski <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Denys Vlasenko <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link:
http://lkml.kernel.org/r/4710be56d76ef994ddf59087aad98c000fbab9a4.1424989793.git.l...@amacapital.net
[ Backported from tip:x86/asm. ]
Signed-off-by: Ingo Molnar <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
arch/x86/kernel/entry_64.S | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -334,11 +334,14 @@ ENTRY(ret_from_fork)
testl $3, CS-ARGOFFSET(%rsp) # from kernel_thread?
jz 1f
- testl $_TIF_IA32, TI_flags(%rcx) # 32-bit compat task needs IRET
- jnz int_ret_from_sys_call
-
- RESTORE_TOP_OF_STACK %rdi, -ARGOFFSET
- jmp ret_from_sys_call # go to the SYSRET fastpath
+ /*
+ * By the time we get here, we have no idea whether our pt_regs,
+ * ti flags, and ti status came from the 64-bit SYSCALL fast path,
+ * the slow path, or one of the ia32entry paths.
+ * Use int_ret_from_sys_call to return, since it can safely handle
+ * all of the above.
+ */
+ jmp int_ret_from_sys_call
1:
subq $REST_SKIP, %rsp # leave space for volatiles
Patches currently in stable-queue which might be from [email protected] are
queue-3.19/x86-asm-entry-64-remove-a-bogus-ret_from_fork-optimization.patch
queue-3.19/net-compat-ignore-msg_cmsg_compat-in-compat_sys_-send-recv-msg.patch
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