Messages in this thread Patch in this message | | | From | Anders Roxell <> | Date | Tue, 21 Sep 2021 12:58:34 +0200 | Subject | Re: [patch V3 15/20] x86/fpu/signal: Change return type of copy_fpregs_to_sigframe() helpers to boolean |
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On Wed, 8 Sept 2021 at 15:30, Thomas Gleixner <tglx@linutronix.de> wrote: > > Now that copy_fpregs_to_sigframe() returns boolean the individual return > codes in the related helper functions do not make sense anymore. Change > them to return boolean success/fail. > > Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
When I build and boot (qemu_x86_64) a defconfig kernel on from todays next tag next-20210921 I see the following segmentation fault
2021-09-21T10:11:45 <6>[ 1.622922] mount (89) used greatest stack depth: 14384 bytes left 2021-09-21T10:11:45 <6>[ 1.664760] EXT4-fs (sda): re-mounted. Opts: (null). Quota mode: none. 2021-09-21T10:11:45 <6>[ 1.691041] mkdir (92) used greatest stack depth: 14312 bytes left 2021-09-21T10:11:45 <6>[ 1.713201] mount (93) used greatest stack depth: 13720 bytes left 2021-09-21T10:11:46 Starting syslogd: /etc/init.d/rcS: line 12: 101 Segmentation fault $i start
I did a bisection and found this as the faulty patch [1]. When I revert this patch I can't see the issue.
We noticed that function 'save_xstate_epilog()' changes the polarity of its return code for one of the return statements, and for its only caller. but not for the other return statement.
I tried this patch and I couldn't see the segmentation fault.
diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c index 445c57c9c539..61eeebc04427 100644 --- a/arch/x86/kernel/fpu/signal.c +++ b/arch/x86/kernel/fpu/signal.c @@ -104,7 +104,7 @@ static inline int save_xstate_epilog(void __user *buf, int ia32_frame) err = __copy_to_user(&x->i387.sw_reserved, sw_bytes, sizeof(*sw_bytes));
if (!use_xsave()) - return err; + return !err;
err |= __put_user(FP_XSTATE_MAGIC2, (__u32 __user *)(buf + fpu_user_xstate_size));
Cheers, Anders [1] http://ix.io/3zxf
> --- > arch/x86/kernel/fpu/signal.c | 17 +++++++++-------- > 1 file changed, 9 insertions(+), 8 deletions(-) > > --- a/arch/x86/kernel/fpu/signal.c > +++ b/arch/x86/kernel/fpu/signal.c > @@ -65,7 +65,7 @@ static inline int check_xstate_in_sigfra > /* > * Signal frame handlers. > */ > -static inline int save_fsave_header(struct task_struct *tsk, void __user *buf) > +static inline bool save_fsave_header(struct task_struct *tsk, void __user *buf) > { > if (use_fxsr()) { > struct xregs_state *xsave = &tsk->thread.fpu.state.xsave; > @@ -82,18 +82,19 @@ static inline int save_fsave_header(stru > if (__copy_to_user(buf, &env, sizeof(env)) || > __put_user(xsave->i387.swd, &fp->status) || > __put_user(X86_FXSR_MAGIC, &fp->magic)) > - return -1; > + return false; > } else { > struct fregs_state __user *fp = buf; > u32 swd; > + > if (__get_user(swd, &fp->swd) || __put_user(swd, &fp->status)) > - return -1; > + return false; > } > > - return 0; > + return true; > } > > -static inline int save_xstate_epilog(void __user *buf, int ia32_frame) > +static inline bool save_xstate_epilog(void __user *buf, int ia32_frame) > { > struct xregs_state __user *x = buf; > struct _fpx_sw_bytes *sw_bytes; > @@ -131,7 +132,7 @@ static inline int save_xstate_epilog(voi > > err |= __put_user(xfeatures, (__u32 __user *)&x->header.xfeatures); > > - return err; > + return !err; > } > > static inline int copy_fpregs_to_sigframe(struct xregs_state __user *buf) > @@ -219,10 +220,10 @@ bool copy_fpstate_to_sigframe(void __use > } > > /* Save the fsave header for the 32-bit frames. */ > - if ((ia32_fxstate || !use_fxsr()) && save_fsave_header(tsk, buf)) > + if ((ia32_fxstate || !use_fxsr()) && !save_fsave_header(tsk, buf)) > return false; > > - if (use_fxsr() && save_xstate_epilog(buf_fx, ia32_fxstate)) > + if (use_fxsr() && !save_xstate_epilog(buf_fx, ia32_fxstate)) > return false; > > return true; >
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