diff options
author | Christoph Hellwig <hch@lst.de> | 2020-06-09 07:34:50 +0300 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-06-09 19:39:15 +0300 |
commit | 98a23609b10364a51a1bb3688f8dd1cd1aa94a9a (patch) | |
tree | 8cf32f92fccd8cd5264434d42fa68dcba4c2ab3c /mm | |
parent | 7676fbf21b5fa04341c8046c2cbcd1949293e7ec (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.c | 10 | ||||
-rw-r--r-- | mm/maccess.c | 40 |
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); |