Messages in this thread Patch in this message | | | Date | Fri, 29 Sep 2023 13:33:50 +0200 (CEST) | From | Sebastian Ott <> | Subject | Re: [PATCH v4 0/6] binfmt_elf: Support segments with 0 filesz and misaligned starts |
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Hello Kees,
On Thu, 28 Sep 2023, Kees Cook wrote: > This is the continuation of the work Eric started for handling > "p_memsz > p_filesz" in arbitrary segments (rather than just the last, > BSS, segment). I've added the suggested changes: > > - drop unused "elf_bss" variable > - refactor load_elf_interp() to use elf_load() > - refactor load_elf_library() to use elf_load() > - report padzero() errors when PROT_WRITE is present > - drop vm_brk()
While I was debugging the initial issue I stumbled over the following - care to take it as part of this series?
----->8 [PATCH] mm: vm_brk_flags don't bail out while holding lock
Calling vm_brk_flags() with flags set other than VM_EXEC will exit the function without releasing the mmap_write_lock.
Just do the sanity check before the lock is acquired. This doesn't fix an actual issue since no caller sets a flag other than VM_EXEC.
Cc: Andrew Morton <akpm@linux-foundation.org> Cc: linux-mm@kvack.org Signed-off-by: Sebastian Ott <sebott@redhat.com> --- mm/mmap.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/mm/mmap.c b/mm/mmap.c index b56a7f0c9f85..7ed286662839 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -3143,13 +3143,13 @@ int vm_brk_flags(unsigned long addr, unsigned long request, unsigned long flags) if (!len) return 0;
- if (mmap_write_lock_killable(mm)) - return -EINTR; - /* Until we need other flags, refuse anything except VM_EXEC. */ if ((flags & (~VM_EXEC)) != 0) return -EINVAL;
+ if (mmap_write_lock_killable(mm)) + return -EINTR; + ret = check_brk_limits(addr, len); if (ret) goto limits_failed; -- 2.41.0
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