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Merge branch 'gate-page-refcount' (patches from Dave Hansen)

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Merge gate page refcount fix from Dave Hansen:
 "During the conversion over to pin_user_pages(), gate pages were missed.

  The fix is pretty simple, and is accompanied by a new test from Andy
  which probably would have caught this earlier"

* emailed patches from Dave Hansen <dave.hansen@linux.intel.com>:
  selftests/x86/test_vsyscall: Improve the process_vm_readv() test
  mm: fix pin vs. gup mismatch with gate pages
This commit is contained in:
Linus Torvalds 2020-09-03 18:43:06 -07:00
commit 8381979dfa
2 changed files with 21 additions and 3 deletions
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2
mm/gup.c
View File

@ -843,7 +843,7 @@ static int get_gate_page(struct mm_struct *mm, unsigned long address,
goto unmap;
*page = pte_page(*pte);
}
if (unlikely(!try_get_page(*page))) {
if (unlikely(!try_grab_page(*page, gup_flags))) {
ret = -ENOMEM;
goto unmap;
}

22
tools/testing/selftests/x86/test_vsyscall.c
View File

@ -462,6 +462,17 @@ static int test_vsys_x(void)
return 0;
}
/*
* Debuggers expect ptrace() to be able to peek at the vsyscall page.
* Use process_vm_readv() as a proxy for ptrace() to test this. We
* want it to work in the vsyscall=emulate case and to fail in the
* vsyscall=xonly case.
*
* It's worth noting that this ABI is a bit nutty. write(2) can't
* read from the vsyscall page on any kernel version or mode. The
* fact that ptrace() ever worked was a nice courtesy of old kernels,
* but the code to support it is fairly gross.
*/
static int test_process_vm_readv(void)
{
#ifdef __x86_64__
@ -477,8 +488,12 @@ static int test_process_vm_readv(void)
remote.iov_len = 4096;
ret = process_vm_readv(getpid(), &local, 1, &remote, 1, 0);
if (ret != 4096) {
printf("[OK]\tprocess_vm_readv() failed (ret = %d, errno = %d)\n", ret, errno);
return 0;
/*
* We expect process_vm_readv() to work if and only if the
* vsyscall page is readable.
*/
printf("[%s]\tprocess_vm_readv() failed (ret = %d, errno = %d)\n", vsyscall_map_r ? "FAIL" : "OK", ret, errno);
return vsyscall_map_r ? 1 : 0;
}
if (vsyscall_map_r) {
@ -488,6 +503,9 @@ static int test_process_vm_readv(void)
printf("[FAIL]\tIt worked but returned incorrect data\n");
return 1;
}
} else {
printf("[FAIL]\tprocess_rm_readv() succeeded, but it should have failed in this configuration\n");
return 1;
}
#endif