m68k: Move signal frame following exception on 68020/030
stable inclusion from stable-v5.10.181 commit 89eba5586aa4d308a11b5246f5286abb73c7796d category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I8GJZJ Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=89eba5586aa4d308a11b5246f5286abb73c7796d -------------------------------- commit b845b574 upstream. On 68030/020, an instruction such as, moveml %a2-%a3/%a5,%sp@- may cause a stack page fault during instruction execution (i.e. not at an instruction boundary) and produce a format 0xB exception frame. In this situation, the value of USP will be unreliable. If a signal is to be delivered following the exception, this USP value is used to calculate the location for a signal frame. This can result in a corrupted user stack. The corruption was detected in dash (actually in glibc) where it showed up as an intermittent "stack smashing detected" message and crash following signal delivery for SIGCHLD. It was hard to reproduce that failure because delivery of the signal raced with the page fault and because the kernel places an unpredictable gap of up to 7 bytes between the USP and the signal frame. A format 0xB exception frame can be produced by a bus error or an address error. The 68030 Users Manual says that address errors occur immediately upon detection during instruction prefetch. The instruction pipeline allows prefetch to overlap with other instructions, which means an address error can arise during the execution of a different instruction. So it seems likely that this patch may help in the address error case also. Reported-and-tested-by:Stan Johnson <userm57@yahoo.com> Link: https://lore.kernel.org/all/CAMuHMdW3yD22_ApemzW_6me3adq6A458u1_F0v-1EYwK_62jPA@mail.gmail.com/ Cc: Michael Schmitz <schmitzmic@gmail.com> Cc: Andreas Schwab <schwab@linux-m68k.org> Cc: stable@vger.kernel.org Co-developed-by:
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