AuxXxilium/linux_dsm_epyc7002
1
0
Fork 0
mirror of https://github.com/AuxXxilium/linux_dsm_epyc7002.git synced 2024-11-25 06:50:52 +07:00
Code Issues Actions Packages Projects Releases Wiki Activity

[POWERPC] Fix subtle FP state corruption bug in signal return on SMP

Browse Source 
This fixes a bug which can cause corruption of the floating-point state
on return from a signal handler.  If we have a signal handler that has
used the floating-point registers, and it happens to context-switch to
another task while copying the interrupted floating-point state from the
user stack into the thread struct (e.g. because of a page fault, or
because it gets preempted), the context switch code will think that the
FP registers contain valid FP state that needs to be copied into the
thread_struct, and will thus overwrite the values that the signal return
code has put into the thread_struct.

This can occur because we clear the MSR bits that indicate the presence
of valid FP state after copying the state into the thread_struct.  To fix
this we just move the clearing of the MSR bits to before the copy.  A
similar potential problem also occurs with the Altivec state, and this
fixes that in the same way.

Signed-off-by: Paul Mackerras <paulus@samba.org>
This commit is contained in:
Paul Mackerras 2007-06-26 14:49:11 +10:00
parent 74609f4536
commit ae62fbb5f1
1 changed files with 7 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
arch/powerpc/kernel/signal_64.c
View File

@ -176,6 +176,13 @@ static long restore_sigcontext(struct pt_regs *regs, sigset_t *set, int sig,
*/
discard_lazy_cpu_state();
/*
* Force reload of FP/VEC.
* This has to be done before copying stuff into current->thread.fpr/vr
* for the reasons explained in the previous comment.
*/
regs->msr &= ~(MSR_FP | MSR_FE0 | MSR_FE1 | MSR_VEC);
err |= __copy_from_user(&current->thread.fpr, &sc->fp_regs, FP_REGS_SIZE);
#ifdef CONFIG_ALTIVEC
@ -197,9 +204,6 @@ static long restore_sigcontext(struct pt_regs *regs, sigset_t *set, int sig,
current->thread.vrsave = 0;
#endif /* CONFIG_ALTIVEC */
/* Force reload of FP/VEC */
regs->msr &= ~(MSR_FP | MSR_FE0 | MSR_FE1 | MSR_VEC);
return err;
}