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authorAlexei Starovoitov <ast@kernel.org>2020-05-15 08:10:36 -0700
committerAlexei Starovoitov <ast@kernel.org>2020-05-15 08:15:07 -0700
commit59df9f1fb4977b40cfad8d07b0d5baeb3a07e22c (patch)
treebb520b4c58247f567a586756c98ab5840d21f8f8
parent6d74f64b922b8394dccc52576659cb0dc0a1da7b (diff)
parentb2a5212fb634561bb734c6356904e37f6665b955 (diff)
downloadlinux-59df9f1fb4977b40cfad8d07b0d5baeb3a07e22c.tar.gz
Merge branch 'restrict-bpf_probe_read'
Daniel Borkmann says: ==================== Small set of fixes in order to restrict BPF helpers for tracing which are broken on archs with overlapping address ranges as per discussion in [0]. I've targetted this for -bpf tree so they can be routed as fixes. Thanks! v1 -> v2: - switch to reusable %pks, %pus format specifiers (Yonghong) - fixate %s on kernel_ds probing for archs with overlapping addr space [0] https://lore.kernel.org/bpf/CAHk-=wjJKo0GVixYLmqPn-Q22WFu0xHaBSjKEo7e7Yw72y5SPQ@mail.gmail.com/T/ ==================== Signed-off-by: Alexei Starovoitov <ast@kernel.org>
-rw-r--r--Documentation/core-api/printk-formats.rst14
-rw-r--r--arch/arm/Kconfig1
-rw-r--r--arch/arm64/Kconfig1
-rw-r--r--arch/x86/Kconfig1
-rw-r--r--init/Kconfig3
-rw-r--r--kernel/bpf/verifier.c4
-rw-r--r--kernel/trace/bpf_trace.c100
-rw-r--r--lib/vsprintf.c12
8 files changed, 101 insertions, 35 deletions
diff --git a/Documentation/core-api/printk-formats.rst b/Documentation/core-api/printk-formats.rst
index 8ebe46b1af39..5dfcc4592b23 100644
--- a/Documentation/core-api/printk-formats.rst
+++ b/Documentation/core-api/printk-formats.rst
@@ -112,6 +112,20 @@ used when printing stack backtraces. The specifier takes into
consideration the effect of compiler optimisations which may occur
when tail-calls are used and marked with the noreturn GCC attribute.
+Probed Pointers from BPF / tracing
+----------------------------------
+
+::
+
+ %pks kernel string
+ %pus user string
+
+The ``k`` and ``u`` specifiers are used for printing prior probed memory from
+either kernel memory (k) or user memory (u). The subsequent ``s`` specifier
+results in printing a string. For direct use in regular vsnprintf() the (k)
+and (u) annotation is ignored, however, when used out of BPF's bpf_trace_printk(),
+for example, it reads the memory it is pointing to without faulting.
+
Kernel Pointers
---------------
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 66a04f6f4775..c77c93c485a0 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -12,6 +12,7 @@ config ARM
select ARCH_HAS_KEEPINITRD
select ARCH_HAS_KCOV
select ARCH_HAS_MEMBARRIER_SYNC_CORE
+ select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
select ARCH_HAS_PTE_SPECIAL if ARM_LPAE
select ARCH_HAS_PHYS_TO_DMA
select ARCH_HAS_SETUP_DMA_OPS
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 40fb05d96c60..5d513f461957 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -20,6 +20,7 @@ config ARM64
select ARCH_HAS_KCOV
select ARCH_HAS_KEEPINITRD
select ARCH_HAS_MEMBARRIER_SYNC_CORE
+ select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
select ARCH_HAS_PTE_DEVMAP
select ARCH_HAS_PTE_SPECIAL
select ARCH_HAS_SETUP_DMA_OPS
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 1197b5596d5a..2d3f963fd6f1 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -68,6 +68,7 @@ config X86
select ARCH_HAS_KCOV if X86_64
select ARCH_HAS_MEM_ENCRYPT
select ARCH_HAS_MEMBARRIER_SYNC_CORE
+ select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
select ARCH_HAS_PMEM_API if X86_64
select ARCH_HAS_PTE_DEVMAP if X86_64
select ARCH_HAS_PTE_SPECIAL
diff --git a/init/Kconfig b/init/Kconfig
index 9e22ee8fbd75..6fd13a051342 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -2279,6 +2279,9 @@ config ASN1
source "kernel/Kconfig.locks"
+config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
+ bool
+
config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
bool
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index a44ba6672688..8d7ee40e2748 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -4340,7 +4340,9 @@ static void do_refine_retval_range(struct bpf_reg_state *regs, int ret_type,
if (ret_type != RET_INTEGER ||
(func_id != BPF_FUNC_get_stack &&
- func_id != BPF_FUNC_probe_read_str))
+ func_id != BPF_FUNC_probe_read_str &&
+ func_id != BPF_FUNC_probe_read_kernel_str &&
+ func_id != BPF_FUNC_probe_read_user_str))
return;
ret_reg->smax_value = meta->msize_max_value;
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index ca1796747a77..a010edc37ee0 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -323,17 +323,15 @@ static const struct bpf_func_proto *bpf_get_probe_write_proto(void)
/*
* Only limited trace_printk() conversion specifiers allowed:
- * %d %i %u %x %ld %li %lu %lx %lld %lli %llu %llx %p %s
+ * %d %i %u %x %ld %li %lu %lx %lld %lli %llu %llx %p %pks %pus %s
*/
BPF_CALL_5(bpf_trace_printk, char *, fmt, u32, fmt_size, u64, arg1,
u64, arg2, u64, arg3)
{
+ int i, mod[3] = {}, fmt_cnt = 0;
+ char buf[64], fmt_ptype;
+ void *unsafe_ptr = NULL;
bool str_seen = false;
- int mod[3] = {};
- int fmt_cnt = 0;
- u64 unsafe_addr;
- char buf[64];
- int i;
/*
* bpf_check()->check_func_arg()->check_stack_boundary()
@@ -359,40 +357,71 @@ BPF_CALL_5(bpf_trace_printk, char *, fmt, u32, fmt_size, u64, arg1,
if (fmt[i] == 'l') {
mod[fmt_cnt]++;
i++;
- } else if (fmt[i] == 'p' || fmt[i] == 's') {
+ } else if (fmt[i] == 'p') {
mod[fmt_cnt]++;
+ if ((fmt[i + 1] == 'k' ||
+ fmt[i + 1] == 'u') &&
+ fmt[i + 2] == 's') {
+ fmt_ptype = fmt[i + 1];
+ i += 2;
+ goto fmt_str;
+ }
+
/* disallow any further format extensions */
if (fmt[i + 1] != 0 &&
!isspace(fmt[i + 1]) &&
!ispunct(fmt[i + 1]))
return -EINVAL;
- fmt_cnt++;
- if (fmt[i] == 's') {
- if (str_seen)
- /* allow only one '%s' per fmt string */
- return -EINVAL;
- str_seen = true;
-
- switch (fmt_cnt) {
- case 1:
- unsafe_addr = arg1;
- arg1 = (long) buf;
- break;
- case 2:
- unsafe_addr = arg2;
- arg2 = (long) buf;
- break;
- case 3:
- unsafe_addr = arg3;
- arg3 = (long) buf;
- break;
- }
- buf[0] = 0;
- strncpy_from_unsafe(buf,
- (void *) (long) unsafe_addr,
+
+ goto fmt_next;
+ } else if (fmt[i] == 's') {
+ mod[fmt_cnt]++;
+ fmt_ptype = fmt[i];
+fmt_str:
+ if (str_seen)
+ /* allow only one '%s' per fmt string */
+ return -EINVAL;
+ str_seen = true;
+
+ if (fmt[i + 1] != 0 &&
+ !isspace(fmt[i + 1]) &&
+ !ispunct(fmt[i + 1]))
+ return -EINVAL;
+
+ switch (fmt_cnt) {
+ case 0:
+ unsafe_ptr = (void *)(long)arg1;
+ arg1 = (long)buf;
+ break;
+ case 1:
+ unsafe_ptr = (void *)(long)arg2;
+ arg2 = (long)buf;
+ break;
+ case 2:
+ unsafe_ptr = (void *)(long)arg3;
+ arg3 = (long)buf;
+ break;
+ }
+
+ buf[0] = 0;
+ switch (fmt_ptype) {
+ case 's':
+#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
+ strncpy_from_unsafe(buf, unsafe_ptr,
sizeof(buf));
+ break;
+#endif
+ case 'k':
+ strncpy_from_unsafe_strict(buf, unsafe_ptr,
+ sizeof(buf));
+ break;
+ case 'u':
+ strncpy_from_unsafe_user(buf,
+ (__force void __user *)unsafe_ptr,
+ sizeof(buf));
+ break;
}
- continue;
+ goto fmt_next;
}
if (fmt[i] == 'l') {
@@ -403,6 +432,7 @@ BPF_CALL_5(bpf_trace_printk, char *, fmt, u32, fmt_size, u64, arg1,
if (fmt[i] != 'i' && fmt[i] != 'd' &&
fmt[i] != 'u' && fmt[i] != 'x')
return -EINVAL;
+fmt_next:
fmt_cnt++;
}
@@ -825,14 +855,16 @@ bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
return &bpf_probe_read_user_proto;
case BPF_FUNC_probe_read_kernel:
return &bpf_probe_read_kernel_proto;
- case BPF_FUNC_probe_read:
- return &bpf_probe_read_compat_proto;
case BPF_FUNC_probe_read_user_str:
return &bpf_probe_read_user_str_proto;
case BPF_FUNC_probe_read_kernel_str:
return &bpf_probe_read_kernel_str_proto;
+#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
+ case BPF_FUNC_probe_read:
+ return &bpf_probe_read_compat_proto;
case BPF_FUNC_probe_read_str:
return &bpf_probe_read_compat_str_proto;
+#endif
#ifdef CONFIG_CGROUPS
case BPF_FUNC_get_current_cgroup_id:
return &bpf_get_current_cgroup_id_proto;
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 7c488a1ce318..532b6606a18a 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -2168,6 +2168,10 @@ char *fwnode_string(char *buf, char *end, struct fwnode_handle *fwnode,
* f full name
* P node name, including a possible unit address
* - 'x' For printing the address. Equivalent to "%lx".
+ * - '[ku]s' For a BPF/tracing related format specifier, e.g. used out of
+ * bpf_trace_printk() where [ku] prefix specifies either kernel (k)
+ * or user (u) memory to probe, and:
+ * s a string, equivalent to "%s" on direct vsnprintf() use
*
* ** When making changes please also update:
* Documentation/core-api/printk-formats.rst
@@ -2251,6 +2255,14 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
if (!IS_ERR(ptr))
break;
return err_ptr(buf, end, ptr, spec);
+ case 'u':
+ case 'k':
+ switch (fmt[1]) {
+ case 's':
+ return string(buf, end, ptr, spec);
+ default:
+ return error_string(buf, end, "(einval)", spec);
+ }
}
/* default is to _not_ leak addresses, hash before printing */