linux/fs/proc
Miles Chen 40d6366e9d proc: use untagged_addr() for pagemap_read addresses
When we try to visit the pagemap of a tagged userspace pointer, we find
that the start_vaddr is not correct because of the tag.
To fix it, we should untag the userspace pointers in pagemap_read().

I tested with 5.10-rc4 and the issue remains.

Explanation from Catalin in [1]:

 "Arguably, that's a user-space bug since tagged file offsets were never
  supported. In this case it's not even a tag at bit 56 as per the arm64
  tagged address ABI but rather down to bit 47. You could say that the
  problem is caused by the C library (malloc()) or whoever created the
  tagged vaddr and passed it to this function. It's not a kernel
  regression as we've never supported it.

  Now, pagemap is a special case where the offset is usually not
  generated as a classic file offset but rather derived by shifting a
  user virtual address. I guess we can make a concession for pagemap
  (only) and allow such offset with the tag at bit (56 - PAGE_SHIFT + 3)"

My test code is based on [2]:

A userspace pointer which has been tagged by 0xb4: 0xb400007662f541c8

userspace program:

  uint64 OsLayer::VirtualToPhysical(void *vaddr) {
	uint64 frame, paddr, pfnmask, pagemask;
	int pagesize = sysconf(_SC_PAGESIZE);
	off64_t off = ((uintptr_t)vaddr) / pagesize * 8; // off = 0xb400007662f541c8 / pagesize * 8 = 0x5a00003b317aa0
	int fd = open(kPagemapPath, O_RDONLY);
	...

	if (lseek64(fd, off, SEEK_SET) != off || read(fd, &frame, 8) != 8) {
		int err = errno;
		string errtxt = ErrorString(err);
		if (fd >= 0)
			close(fd);
		return 0;
	}
  ...
  }

kernel fs/proc/task_mmu.c:

  static ssize_t pagemap_read(struct file *file, char __user *buf,
		size_t count, loff_t *ppos)
  {
	...
	src = *ppos;
	svpfn = src / PM_ENTRY_BYTES; // svpfn == 0xb400007662f54
	start_vaddr = svpfn << PAGE_SHIFT; // start_vaddr == 0xb400007662f54000
	end_vaddr = mm->task_size;

	/* watch out for wraparound */
	// svpfn == 0xb400007662f54
	// (mm->task_size >> PAGE) == 0x8000000
	if (svpfn > mm->task_size >> PAGE_SHIFT) // the condition is true because of the tag 0xb4
		start_vaddr = end_vaddr;

	ret = 0;
	while (count && (start_vaddr < end_vaddr)) { // we cannot visit correct entry because start_vaddr is set to end_vaddr
		int len;
		unsigned long end;
		...
	}
	...
  }

[1] https://lore.kernel.org/patchwork/patch/1343258/
[2] https://github.com/stressapptest/stressapptest/blob/master/src/os.cc#L158

Link: https://lkml.kernel.org/r/20201204024347.8295-1-miles.chen@mediatek.com
Signed-off-by: Miles Chen <miles.chen@mediatek.com>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Will Deacon <will@kernel.org>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Song Bao Hua (Barry Song) <song.bao.hua@hisilicon.com>
Cc: <stable@vger.kernel.org>	[5.4-]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-12-11 14:02:14 -08:00
..
array.c seccomp: Report number of loaded filters in /proc/$pid/status 2020-07-10 16:01:51 -07:00
base.c mm, oom: keep oom_adj under or at upper limit when printing 2020-11-02 12:14:19 -08:00
bootconfig.c proc/bootconfig: Fix to use correct quotes for value 2020-06-16 21:21:03 -04:00
cmdline.c proc: introduce proc_create_single{,_data} 2018-05-16 07:23:35 +02:00
consoles.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 191 2019-05-30 11:29:21 -07:00
cpuinfo.c proc/cpuinfo: switch to ->read_iter 2020-11-06 10:05:18 -08:00
devices.c block: move block-related definitions out of fs.h 2020-06-24 09:16:02 -06:00
fd.c proc: use "unsigned int" in proc_fill_cache() 2018-06-07 17:34:38 -07:00
fd.h
generic.c proc "seq files": switch to ->read_iter 2020-11-06 10:05:18 -08:00
inode.c proc: wire up generic_file_splice_read for iter ops 2020-11-06 10:05:18 -08:00
internal.h proc: faster open/read/close with "permanent" files 2020-04-07 10:43:42 -07:00
interrupts.c proc: introduce proc_create_seq{,_data} 2018-05-16 07:23:35 +02:00
Kconfig treewide: replace '---help---' in Kconfig files with 'help' 2020-06-14 01:57:21 +09:00
kcore.c maccess: rename probe_kernel_{read,write} to copy_{from,to}_kernel_nofault 2020-06-17 10:57:41 -07:00
kmsg.c proc: faster open/read/close with "permanent" files 2020-04-07 10:43:42 -07:00
loadavg.c sched: loadavg: consolidate LOAD_INT, LOAD_FRAC, CALC_LOAD 2018-10-26 16:26:32 -07:00
Makefile proc: bootconfig: Add /proc/bootconfig to show boot config list 2020-01-13 13:19:39 -05:00
meminfo.c proc/meminfo: avoid open coded reading of vm_committed_as 2020-08-07 11:33:26 -07:00
namespaces.c Merge branch 'work.openat2' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-01-29 11:20:24 -08:00
nommu.c mm: don't include asm/pgtable.h if linux/mm.h is already included 2020-06-09 09:39:13 -07:00
page.c mm: Add PG_arch_2 page flag 2020-09-04 12:46:06 +01:00
proc_net.c bpf: Refactor to provide aux info to bpf_iter_init_seq_priv_t 2020-07-25 20:16:32 -07:00
proc_sysctl.c sysctl: Convert to iter interfaces 2020-09-08 22:20:39 -04:00
proc_tty.c tty: replace ->proc_fops with ->proc_show 2018-05-16 07:24:30 +02:00
root.c proc: s_fs_info may be NULL when proc_kill_sb is called 2020-06-10 14:54:54 -05:00
self.c proc: don't allow async path resolution of /proc/self components 2020-11-13 16:47:52 -07:00
softirqs.c proc: introduce proc_create_single{,_data} 2018-05-16 07:23:35 +02:00
stat.c proc/stat: switch to ->read_iter 2020-11-06 10:05:18 -08:00
task_mmu.c proc: use untagged_addr() for pagemap_read addresses 2020-12-11 14:02:14 -08:00
task_nommu.c mmap locking API: use coccinelle to convert mmap_sem rwsem call sites 2020-06-09 09:39:14 -07:00
thread_self.c proc: Use new_inode not new_inode_pseudo 2020-06-12 14:13:33 -05:00
uptime.c fs/proc: Respect boottime inside time namespace for /proc/uptime 2020-01-14 12:20:56 +01:00
util.c fs/proc/util.c: include fs/proc/internal.h for name_to_int() 2019-01-04 13:13:45 -08:00
version.c proc: introduce proc_create_single{,_data} 2018-05-16 07:23:35 +02:00
vmcore.c mm: don't include asm/pgtable.h if linux/mm.h is already included 2020-06-09 09:39:13 -07:00