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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 /mm
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>
Diffstat (limited to 'mm')
-rw-r--r--mm/debug.c10
-rw-r--r--mm/maccess.c40
2 files changed, 11 insertions, 39 deletions
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);