On Thu, Aug 13, 2015 at 9:43 AM, Linus Torvalds <torva...@linux-foundation.org> wrote: > On Thu, Aug 13, 2015 at 9:34 AM, Linus Torvalds > <torva...@linux-foundation.org> wrote: >> >> Are you sure? From the description by Stas, the problem is literally >> the *restoring* action of the sigcontext, and trying to restore a SS >> value that is no longer valid. >> >> "The crash happens when DOS program terminates. >> At that point dosemu subverts the execution flow by >> replacing segregs and cs/ip ss/sp in sigcontext with its own. >> But __pad0 still has DOS SS, which crash because (presumably) >> the DOS LDT have been just removed" > > Side note: if this is the main issue, and the problem is the "iret" > faulting when trying to restore SS (and causing an unexpected SIGSEGV > that dosemu crashes on), then an alternate model might be to keep the > save/restore SS code, but do a "VERW" on the SS descriptor in > restore_sigcontext(), and silently just replacing it with __USER_DS if > that fails. >
I have a patch to do approximately that (using LAR instead of VERW to rule out DPL < 3. I'm 90% sure that the regs->ss = __USER_DS thing is a problem. Read farther up in the thread. I'm leaning toward saying we should revert, cc: stable, and fix it better for 4.3. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
