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authorChristoph Hellwig <hch@lst.de>2020-06-08 21:34:50 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-06-09 09:39:15 -0700
commit98a23609b10364a51a1bb3688f8dd1cd1aa94a9a (patch)
tree8cf32f92fccd8cd5264434d42fa68dcba4c2ab3c
parent7676fbf21b5fa04341c8046c2cbcd1949293e7ec (diff)
maccess: always use strict semantics for probe_kernel_read
Except for historical confusion in the kprobes/uprobes and bpf tracers, which has been fixed now, there is no good reason to ever allow user memory accesses from probe_kernel_read. Switch probe_kernel_read to only read from kernel memory. [akpm@linux-foundation.org: update it for "mm, dump_page(): do not crash with invalid mapping pointer"] Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Cc: Alexei Starovoitov <ast@kernel.org> Cc: Daniel Borkmann <daniel@iogearbox.net> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/20200521152301.2587579-17-hch@lst.de Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--arch/parisc/lib/memcpy.c2
-rw-r--r--arch/um/kernel/maccess.c2
-rw-r--r--arch/x86/mm/maccess.c9
-rw-r--r--include/linux/uaccess.h4
-rw-r--r--kernel/trace/bpf_trace.c2
-rw-r--r--kernel/trace/trace_kprobe.c4
-rw-r--r--mm/debug.c10
-rw-r--r--mm/maccess.c40
8 files changed, 19 insertions, 54 deletions
diff --git a/arch/parisc/lib/memcpy.c b/arch/parisc/lib/memcpy.c
index 5b75c35d1da0..94a9fe2702c2 100644
--- a/arch/parisc/lib/memcpy.c
+++ b/arch/parisc/lib/memcpy.c
@@ -57,7 +57,7 @@ void * memcpy(void * dst,const void *src, size_t count)
EXPORT_SYMBOL(raw_copy_in_user);
EXPORT_SYMBOL(memcpy);
-bool probe_kernel_read_allowed(const void *unsafe_src, size_t size, bool strict)
+bool probe_kernel_read_allowed(const void *unsafe_src, size_t size)
{
if ((unsigned long)unsafe_src < PAGE_SIZE)
return false;
diff --git a/arch/um/kernel/maccess.c b/arch/um/kernel/maccess.c
index ad2c538ce497..e929c0966696 100644
--- a/arch/um/kernel/maccess.c
+++ b/arch/um/kernel/maccess.c
@@ -7,7 +7,7 @@
#include <linux/kernel.h>
#include <os.h>
-bool probe_kernel_read_allowed(const void *src, size_t size, bool strict)
+bool probe_kernel_read_allowed(const void *src, size_t size)
{
void *psrc = (void *)rounddown((unsigned long)src, PAGE_SIZE);
diff --git a/arch/x86/mm/maccess.c b/arch/x86/mm/maccess.c
index 86000c1150e8..e1d7d7477c22 100644
--- a/arch/x86/mm/maccess.c
+++ b/arch/x86/mm/maccess.c
@@ -9,13 +9,10 @@ static __always_inline u64 canonical_address(u64 vaddr, u8 vaddr_bits)
return ((s64)vaddr << (64 - vaddr_bits)) >> (64 - vaddr_bits);
}
-bool probe_kernel_read_allowed(const void *unsafe_src, size_t size, bool strict)
+bool probe_kernel_read_allowed(const void *unsafe_src, size_t size)
{
unsigned long vaddr = (unsigned long)unsafe_src;
- if (!strict)
- return true;
-
/*
* Range covering the highest possible canonical userspace address
* as well as non-canonical address range. For the canonical range
@@ -25,10 +22,8 @@ bool probe_kernel_read_allowed(const void *unsafe_src, size_t size, bool strict)
canonical_address(vaddr, boot_cpu_data.x86_virt_bits) == vaddr;
}
#else
-bool probe_kernel_read_allowed(const void *unsafe_src, size_t size, bool strict)
+bool probe_kernel_read_allowed(const void *unsafe_src, size_t size)
{
- if (!strict)
- return true;
return (unsigned long)unsafe_src >= TASK_SIZE_MAX;
}
#endif
diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index 4183e585dee6..dac1db05bf7e 100644
--- a/include/linux/uaccess.h
+++ b/include/linux/uaccess.h
@@ -301,11 +301,9 @@ copy_struct_from_user(void *dst, size_t ksize, const void __user *src,
return 0;
}
-bool probe_kernel_read_allowed(const void *unsafe_src, size_t size,
- bool strict);
+bool probe_kernel_read_allowed(const void *unsafe_src, size_t size);
extern long probe_kernel_read(void *dst, const void *src, size_t size);
-extern long probe_kernel_read_strict(void *dst, const void *src, size_t size);
extern long probe_user_read(void *dst, const void __user *src, size_t size);
extern long notrace probe_kernel_write(void *dst, const void *src, size_t size);
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 59cb19888891..e729c9e587a0 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -196,7 +196,7 @@ bpf_probe_read_kernel_common(void *dst, u32 size, const void *unsafe_ptr)
if (unlikely(ret < 0))
goto fail;
- ret = probe_kernel_read_strict(dst, unsafe_ptr, size);
+ ret = probe_kernel_read(dst, unsafe_ptr, size);
if (unlikely(ret < 0))
goto fail;
return ret;
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 6a23b45613a2..ea8d0b094f1b 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -1222,7 +1222,7 @@ fetch_store_strlen(unsigned long addr)
#endif
do {
- ret = probe_kernel_read_strict(&c, (u8 *)addr + len, 1);
+ ret = probe_kernel_read(&c, (u8 *)addr + len, 1);
len++;
} while (c && ret == 0 && len < MAX_STRING_SIZE);
@@ -1300,7 +1300,7 @@ probe_mem_read(void *dest, void *src, size_t size)
if ((unsigned long)src < TASK_SIZE)
return probe_mem_read_user(dest, src, size);
#endif
- return probe_kernel_read_strict(dest, src, size);
+ return probe_kernel_read(dest, src, size);
}
/* Note that we don't verify it, since the code does not come from user space */
diff --git a/mm/debug.c b/mm/debug.c
index f2ede2df585a..b5b1de8c71ac 100644
--- a/mm/debug.c
+++ b/mm/debug.c
@@ -120,9 +120,9 @@ void __dump_page(struct page *page, const char *reason)
* mapping can be invalid pointer and we don't want to crash
* accessing it, so probe everything depending on it carefully
*/
- if (probe_kernel_read_strict(&host, &mapping->host,
- sizeof(struct inode *)) ||
- probe_kernel_read_strict(&a_ops, &mapping->a_ops,
+ if (probe_kernel_read(&host, &mapping->host,
+ sizeof(struct inode *)) ||
+ probe_kernel_read(&a_ops, &mapping->a_ops,
sizeof(struct address_space_operations *))) {
pr_warn("failed to read mapping->host or a_ops, mapping not a valid kernel address?\n");
goto out_mapping;
@@ -133,7 +133,7 @@ void __dump_page(struct page *page, const char *reason)
goto out_mapping;
}
- if (probe_kernel_read_strict(&dentry_first,
+ if (probe_kernel_read(&dentry_first,
&host->i_dentry.first, sizeof(struct hlist_node *))) {
pr_warn("mapping->a_ops:%ps with invalid mapping->host inode address %px\n",
a_ops, host);
@@ -146,7 +146,7 @@ void __dump_page(struct page *page, const char *reason)
}
dentry_ptr = container_of(dentry_first, struct dentry, d_u.d_alias);
- if (probe_kernel_read_strict(&dentry, dentry_ptr,
+ if (probe_kernel_read(&dentry, dentry_ptr,
sizeof(struct dentry))) {
pr_warn("mapping->aops:%ps with invalid mapping->host->i_dentry.first %px\n",
a_ops, dentry_ptr);
diff --git a/mm/maccess.c b/mm/maccess.c
index 85d124628b0e..253b786b2bf1 100644
--- a/mm/maccess.c
+++ b/mm/maccess.c
@@ -6,36 +6,13 @@
#include <linux/mm.h>
#include <linux/uaccess.h>
-static long __probe_kernel_read(void *dst, const void *src, size_t size,
- bool strict);
-
-bool __weak probe_kernel_read_allowed(const void *unsafe_src, size_t size,
- bool strict)
+bool __weak probe_kernel_read_allowed(const void *unsafe_src, size_t size)
{
return true;
}
/**
- * probe_kernel_read(): safely attempt to read from any location
- * @dst: pointer to the buffer that shall take the data
- * @src: address to read from
- * @size: size of the data chunk
- *
- * Same as probe_kernel_read_strict() except that for architectures with
- * not fully separated user and kernel address spaces this function also works
- * for user address tanges.
- *
- * DO NOT USE THIS FUNCTION - it is broken on architectures with entirely
- * separate kernel and user address spaces, and also a bad idea otherwise.
- */
-long probe_kernel_read(void *dst, const void *src, size_t size)
-{
- return __probe_kernel_read(dst, src, size, false);
-}
-EXPORT_SYMBOL_GPL(probe_kernel_read);
-
-/**
- * probe_kernel_read_strict(): safely attempt to read from kernel-space
+ * probe_kernel_read(): safely attempt to read from kernel-space
* @dst: pointer to the buffer that shall take the data
* @src: address to read from
* @size: size of the data chunk
@@ -48,18 +25,12 @@ EXPORT_SYMBOL_GPL(probe_kernel_read);
* probe_kernel_read() suitable for use within regions where the caller
* already holds mmap_lock, or other locks which nest inside mmap_lock.
*/
-long probe_kernel_read_strict(void *dst, const void *src, size_t size)
-{
- return __probe_kernel_read(dst, src, size, true);
-}
-
-static long __probe_kernel_read(void *dst, const void *src, size_t size,
- bool strict)
+long probe_kernel_read(void *dst, const void *src, size_t size)
{
long ret;
mm_segment_t old_fs = get_fs();
- if (!probe_kernel_read_allowed(src, size, strict))
+ if (!probe_kernel_read_allowed(src, size))
return -EFAULT;
set_fs(KERNEL_DS);
@@ -73,6 +44,7 @@ static long __probe_kernel_read(void *dst, const void *src, size_t size,
return -EFAULT;
return 0;
}
+EXPORT_SYMBOL_GPL(probe_kernel_read);
/**
* probe_user_read(): safely attempt to read from a user-space location
@@ -181,7 +153,7 @@ long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr, long count)
if (unlikely(count <= 0))
return 0;
- if (!probe_kernel_read_allowed(unsafe_addr, count, true))
+ if (!probe_kernel_read_allowed(unsafe_addr, count))
return -EFAULT;
set_fs(KERNEL_DS);