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Subject[PATCH v11 09/14] kernel, arm64: untag user pointers in prctl_set_mm*
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This patch is a part of a series that extends arm64 kernel ABI to allow to
pass tagged user pointers (with the top byte set to something else other
than 0x00) as syscall arguments.

prctl_set_mm() and prctl_set_mm_map() use provided user pointers for vma
lookups, which can only by done with untagged pointers.

Untag user pointers in these functions.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
kernel/sys.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)

diff --git a/kernel/sys.c b/kernel/sys.c
index 12df0e5434b8..8e56d87cc6db 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1993,6 +1993,18 @@ static int prctl_set_mm_map(int opt, const void __user *addr, unsigned long data
if (copy_from_user(&prctl_map, addr, sizeof(prctl_map)))
return -EFAULT;

+ prctl_map->start_code = untagged_addr(prctl_map.start_code);
+ prctl_map->end_code = untagged_addr(prctl_map.end_code);
+ prctl_map->start_data = untagged_addr(prctl_map.start_data);
+ prctl_map->end_data = untagged_addr(prctl_map.end_data);
+ prctl_map->start_brk = untagged_addr(prctl_map.start_brk);
+ prctl_map->brk = untagged_addr(prctl_map.brk);
+ prctl_map->start_stack = untagged_addr(prctl_map.start_stack);
+ prctl_map->arg_start = untagged_addr(prctl_map.arg_start);
+ prctl_map->arg_end = untagged_addr(prctl_map.arg_end);
+ prctl_map->env_start = untagged_addr(prctl_map.env_start);
+ prctl_map->env_end = untagged_addr(prctl_map.env_end);
+
error = validate_prctl_map(&prctl_map);
if (error)
return error;
@@ -2106,6 +2118,8 @@ static int prctl_set_mm(int opt, unsigned long addr,
opt != PR_SET_MM_MAP_SIZE)))
return -EINVAL;

+ addr = untagged_addr(addr);
+
#ifdef CONFIG_CHECKPOINT_RESTORE
if (opt == PR_SET_MM_MAP || opt == PR_SET_MM_MAP_SIZE)
return prctl_set_mm_map(opt, (const void __user *)addr, arg4);
--
2.21.0.360.g471c308f928-goog
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