On Tue, Aug 6, 2024 at 5:49 PM Pedro Falcato <pedro.falcato@xxxxxxxxx> wrote: > > On Tue, Aug 6, 2024 at 11:25 PM Jeff Xu <jeffxu@xxxxxxxxxx> wrote: > > > > On Tue, Aug 6, 2024 at 2:28 PM Pedro Falcato <pedro.falcato@xxxxxxxxx> wrote: > > > > > > Optimize mseal checks by removing the separate can_modify_mm() step, and > > > just doing checks on the individual vmas, when various operations are > > > themselves iterating through the tree. This provides a nice speedup. > > > > > > While I was at it, I found that is_madv_discard() was completely bogus. > > > > > Thanks for catching this! > > Is it possible to separate this fix out from this series and send it > > separately and merge first ? > > Sure. This series is definitely too risky to catch this release, so > sending it out as a fix (tomorrow, it's late here) sounds ok. > Do you mind if I send out a fix ? (I will also include a test case to cover that ) > > > > > Note that my series ignores arch_unmap(), which seems to generally be what we're trending towards[2]. It should > > > be applied on top of any powerpc vdso ->close patch to avoid regressions on the PPC architecture. No other > > > architecture seems to use arch_unmap. > > > > > > Note2: This series does not pass all mseal_tests on my end (test_seal_mremap_move_dontunmap_anyaddr fails twice). But the > > > top of Linus's tree does not pass these for me either (neither does my Arch Linux 6.10.2 kernel), > > > for some reason (mremap regression?). > > > > > I just sync to Linus's main and I was able to run the test (except two > > pkeys related test are skipped because I m on VM) > > Okay. Fun bug. > > I was really confused as to why no one could repro this except me :) > > It looks like recently[1] glibc started consuming the new_address > variadic argument when MREMAP_DONTUNMAP. As to the why, > MREMAP_DONTUNMAP also seems to take new_address as a hint (this is not > documented in the man page, and strace also doesn't know this). > However, this trips up some checks that were always fine before > (because glibc always passed NULL, and musl still does): > > if (offset_in_page(new_addr)) > if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len) > if (addr + old_len > new_addr && new_addr + new_len > addr) > > ^^ These all look at the address without looking at MREMAP_FIXED, and > return -EINVAL if they fail. > > So, test_seal_mremap_move_dontunmap_anyaddr passes 0xdeadbeef For Some > Reason (why are you testing mremap in mseal_test.c??), it trips up > offset_in_page(new_addr) in mremap_to, and we crash and burn. > > As to why no one else could repro this: I guess you're not running a > glibc new enough ;) > That makes sense, mystery resolved. I added sys_ functions for mmap/munmap/mprotect, etc, so that the test does not depend on libc, but I didn't do that for mremap, I think the fix will be to add sys_mremap as well. > [1] https://sourceware.org/git/?p=glibc.git;a=commit;h=6c40cb0e9f893d49dc7caee580a055de53562206 > > -- > Pedro
