diff mbox series

[bpf-next,v1] bpf: Add bpf_copy_from_user_str kfunc

Message ID 20240809212301.3782412-1-linux@jordanrome.com (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series [bpf-next,v1] bpf: Add bpf_copy_from_user_str kfunc | expand

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Commit Message

Jordan Rome Aug. 9, 2024, 9:23 p.m. UTC 
This adds a kfunc wrapper around strncpy_from_user,
which can be called from sleepable BPF programs.

This matches the non-sleepable 'bpf_probe_read_user_str'
helper.

Signed-off-by: Jordan Rome <linux@jordanrome.com>
---
 kernel/bpf/helpers.c                          | 26 +++++++++++++++++++
 .../selftests/bpf/prog_tests/attach_probe.c   |  8 +++---
 .../selftests/bpf/prog_tests/read_vsyscall.c  |  1 +
 .../selftests/bpf/progs/read_vsyscall.c       |  9 ++++++-
 .../selftests/bpf/progs/test_attach_probe.c   | 24 ++++++++++++++---
 5 files changed, 61 insertions(+), 7 deletions(-)

--
2.44.1

Comments

Kui-Feng Lee Aug. 10, 2024, 6:49 a.m. UTC | #1 
On 8/9/24 14:23, Jordan Rome wrote:
> This adds a kfunc wrapper around strncpy_from_user,
> which can be called from sleepable BPF programs.
> 
> This matches the non-sleepable 'bpf_probe_read_user_str'
> helper.
> 
> Signed-off-by: Jordan Rome <linux@jordanrome.com>
> ---
>   kernel/bpf/helpers.c                          | 26 +++++++++++++++++++
>   .../selftests/bpf/prog_tests/attach_probe.c   |  8 +++---
>   .../selftests/bpf/prog_tests/read_vsyscall.c  |  1 +
>   .../selftests/bpf/progs/read_vsyscall.c       |  9 ++++++-
>   .../selftests/bpf/progs/test_attach_probe.c   | 24 ++++++++++++++---
>   5 files changed, 61 insertions(+), 7 deletions(-)
> 
> diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
> index d02ae323996b..455cac7b2631 100644
> --- a/kernel/bpf/helpers.c
> +++ b/kernel/bpf/helpers.c
> @@ -2939,6 +2939,31 @@ __bpf_kfunc void bpf_iter_bits_destroy(struct bpf_iter_bits *it)
>   	bpf_mem_free(&bpf_global_ma, kit->bits);
>   }
> 
> +/**
> + * bpf_copy_from_user_str() - Copy a string from an unsafe user address
> + * @dst:             Destination address, in kernel space.  This buffer must be at
> + *                   least @dst__szk bytes long.
> + * @dst__szk:        Maximum number of bytes to copy, including the trailing NUL.
> + * @unsafe_ptr__ign: Source address, in user space.
> + *
> + * Copies a NUL-terminated string from userspace to BPF space. If user string is
> + * too long this will still ensure zero termination in the dst buffer unless
> + * buffer size is 0.
> + */
> +__bpf_kfunc int bpf_copy_from_user_str(void *dst, u32 dst__szk, const void __user *unsafe_ptr__ign)
> +{
> +	int ret;
> +
> +	if (unlikely(!dst__szk))
> +		return 0;
> +
> +	ret = strncpy_from_user(dst, unsafe_ptr__ign, dst__szk);

Does this function promise dst is null terminated if ret >= 0?
It seems not to have null at the end if the source string is longer than
dst_szk.


> +	if (unlikely(ret < 0))
> +		memset(dst, 0, dst__szk);
> +
> +	return ret;
> +}
> +
>   __bpf_kfunc_end_defs();
> 
>   BTF_KFUNCS_START(generic_btf_ids)
> @@ -3024,6 +3049,7 @@ BTF_ID_FLAGS(func, bpf_preempt_enable)
>   BTF_ID_FLAGS(func, bpf_iter_bits_new, KF_ITER_NEW)
>   BTF_ID_FLAGS(func, bpf_iter_bits_next, KF_ITER_NEXT | KF_RET_NULL)
>   BTF_ID_FLAGS(func, bpf_iter_bits_destroy, KF_ITER_DESTROY)
> +BTF_ID_FLAGS(func, bpf_copy_from_user_str, KF_SLEEPABLE)
>   BTF_KFUNCS_END(common_btf_ids)
> 
>   static const struct btf_kfunc_id_set common_kfunc_set = {
> diff --git a/tools/testing/selftests/bpf/prog_tests/attach_probe.c b/tools/testing/selftests/bpf/prog_tests/attach_probe.c
> index 7175af39134f..329c7862b52d 100644
> --- a/tools/testing/selftests/bpf/prog_tests/attach_probe.c
> +++ b/tools/testing/selftests/bpf/prog_tests/attach_probe.c
> @@ -283,9 +283,11 @@ static void test_uprobe_sleepable(struct test_attach_probe *skel)
>   	trigger_func3();
> 
>   	ASSERT_EQ(skel->bss->uprobe_byname3_sleepable_res, 9, "check_uprobe_byname3_sleepable_res");
> -	ASSERT_EQ(skel->bss->uprobe_byname3_res, 10, "check_uprobe_byname3_res");
> -	ASSERT_EQ(skel->bss->uretprobe_byname3_sleepable_res, 11, "check_uretprobe_byname3_sleepable_res");
> -	ASSERT_EQ(skel->bss->uretprobe_byname3_res, 12, "check_uretprobe_byname3_res");
> +	ASSERT_EQ(skel->bss->uprobe_byname3_str_sleepable_res, 10, "check_uprobe_byname3_str_sleepable_res");
> +	ASSERT_EQ(skel->bss->uprobe_byname3_res, 11, "check_uprobe_byname3_res");
> +	ASSERT_EQ(skel->bss->uretprobe_byname3_sleepable_res, 12, "check_uretprobe_byname3_sleepable_res");
> +	ASSERT_EQ(skel->bss->uretprobe_byname3_str_sleepable_res, 13, "check_uretprobe_byname3_str_sleepable_res");
> +	ASSERT_EQ(skel->bss->uretprobe_byname3_res, 14, "check_uretprobe_byname3_res");
>   }
> 
>   void test_attach_probe(void)
> diff --git a/tools/testing/selftests/bpf/prog_tests/read_vsyscall.c b/tools/testing/selftests/bpf/prog_tests/read_vsyscall.c
> index 3405923fe4e6..c7b9ba8b1d06 100644
> --- a/tools/testing/selftests/bpf/prog_tests/read_vsyscall.c
> +++ b/tools/testing/selftests/bpf/prog_tests/read_vsyscall.c
> @@ -23,6 +23,7 @@ struct read_ret_desc {
>   	{ .name = "probe_read_user_str", .ret = -EFAULT },
>   	{ .name = "copy_from_user", .ret = -EFAULT },
>   	{ .name = "copy_from_user_task", .ret = -EFAULT },
> +	{ .name = "copy_from_user_str", .ret = -EFAULT },
>   };
> 
>   void test_read_vsyscall(void)
> diff --git a/tools/testing/selftests/bpf/progs/read_vsyscall.c b/tools/testing/selftests/bpf/progs/read_vsyscall.c
> index 986f96687ae1..27de1e907754 100644
> --- a/tools/testing/selftests/bpf/progs/read_vsyscall.c
> +++ b/tools/testing/selftests/bpf/progs/read_vsyscall.c
> @@ -1,5 +1,6 @@
>   // SPDX-License-Identifier: GPL-2.0
>   /* Copyright (C) 2024. Huawei Technologies Co., Ltd */
> +#include "vmlinux.h"
>   #include <linux/types.h>
>   #include <bpf/bpf_helpers.h>
> 
> @@ -7,10 +8,15 @@
> 
>   int target_pid = 0;
>   void *user_ptr = 0;
> -int read_ret[8];
> +int read_ret[9];
> 
>   char _license[] SEC("license") = "GPL";
> 
> +/*
> + * This is the only kfunc, the others are helpers
> + */
> +int bpf_copy_from_user_str(void *dst, u32, const void *) __weak __ksym;
> +
>   SEC("fentry/" SYS_PREFIX "sys_nanosleep")
>   int do_probe_read(void *ctx)
>   {
> @@ -40,6 +46,7 @@ int do_copy_from_user(void *ctx)
>   	read_ret[6] = bpf_copy_from_user(buf, sizeof(buf), user_ptr);
>   	read_ret[7] = bpf_copy_from_user_task(buf, sizeof(buf), user_ptr,
>   					      bpf_get_current_task_btf(), 0);
> +	read_ret[8] = bpf_copy_from_user_str((char *)buf, sizeof(buf), user_ptr);
> 
>   	return 0;
>   }
> diff --git a/tools/testing/selftests/bpf/progs/test_attach_probe.c b/tools/testing/selftests/bpf/progs/test_attach_probe.c
> index 68466a6ad18c..a90fa0bf103b 100644
> --- a/tools/testing/selftests/bpf/progs/test_attach_probe.c
> +++ b/tools/testing/selftests/bpf/progs/test_attach_probe.c
> @@ -14,11 +14,15 @@ int uretprobe_byname_res = 0;
>   int uprobe_byname2_res = 0;
>   int uretprobe_byname2_res = 0;
>   int uprobe_byname3_sleepable_res = 0;
> +int uprobe_byname3_str_sleepable_res = 0;
>   int uprobe_byname3_res = 0;
>   int uretprobe_byname3_sleepable_res = 0;
> +int uretprobe_byname3_str_sleepable_res = 0;
>   int uretprobe_byname3_res = 0;
>   void *user_ptr = 0;
> 
> +int bpf_copy_from_user_str(void *dst, u32, const void *) __weak __ksym;
> +
>   SEC("ksyscall/nanosleep")
>   int BPF_KSYSCALL(handle_kprobe_auto, struct __kernel_timespec *req, struct __kernel_timespec *rem)
>   {
> @@ -87,11 +91,23 @@ static __always_inline bool verify_sleepable_user_copy(void)
>   	return bpf_strncmp(data, sizeof(data), "test_data") == 0;
>   }
> 
> +static __always_inline bool verify_sleepable_user_copy_str(void)
> +{
> +	int ret;
> +	char data[10];
> +
> +	ret = bpf_copy_from_user_str(data, sizeof(data), user_ptr);
> +
> +	return bpf_strncmp(data, sizeof(data), "test_data") == 0 && ret == 9;
> +}
> +
>   SEC("uprobe.s//proc/self/exe:trigger_func3")
>   int handle_uprobe_byname3_sleepable(struct pt_regs *ctx)
>   {
>   	if (verify_sleepable_user_copy())
>   		uprobe_byname3_sleepable_res = 9;
> +	if (verify_sleepable_user_copy_str())
> +		uprobe_byname3_str_sleepable_res = 10;
>   	return 0;
>   }
> 
> @@ -102,7 +118,7 @@ int handle_uprobe_byname3_sleepable(struct pt_regs *ctx)
>   SEC("uprobe//proc/self/exe:trigger_func3")
>   int handle_uprobe_byname3(struct pt_regs *ctx)
>   {
> -	uprobe_byname3_res = 10;
> +	uprobe_byname3_res = 11;
>   	return 0;
>   }
> 
> @@ -110,14 +126,16 @@ SEC("uretprobe.s//proc/self/exe:trigger_func3")
>   int handle_uretprobe_byname3_sleepable(struct pt_regs *ctx)
>   {
>   	if (verify_sleepable_user_copy())
> -		uretprobe_byname3_sleepable_res = 11;
> +		uretprobe_byname3_sleepable_res = 12;
> +	if (verify_sleepable_user_copy_str())
> +		uretprobe_byname3_str_sleepable_res = 13;
>   	return 0;
>   }
> 
>   SEC("uretprobe//proc/self/exe:trigger_func3")
>   int handle_uretprobe_byname3(struct pt_regs *ctx)
>   {
> -	uretprobe_byname3_res = 12;
> +	uretprobe_byname3_res = 14;
>   	return 0;
>   }
> 
> --
> 2.44.1
> 
>
Jordan Rome Aug. 11, 2024, 9:08 p.m. UTC | #2 
On Sat, Aug 10, 2024 at 2:49 AM Kui-Feng Lee <sinquersw@gmail.com> wrote:
>
>
>
> On 8/9/24 14:23, Jordan Rome wrote:
> > This adds a kfunc wrapper around strncpy_from_user,
> > which can be called from sleepable BPF programs.
> >
> > This matches the non-sleepable 'bpf_probe_read_user_str'
> > helper.
> >
> > Signed-off-by: Jordan Rome <linux@jordanrome.com>
> > ---
> >   kernel/bpf/helpers.c                          | 26 +++++++++++++++++++
> >   .../selftests/bpf/prog_tests/attach_probe.c   |  8 +++---
> >   .../selftests/bpf/prog_tests/read_vsyscall.c  |  1 +
> >   .../selftests/bpf/progs/read_vsyscall.c       |  9 ++++++-
> >   .../selftests/bpf/progs/test_attach_probe.c   | 24 ++++++++++++++---
> >   5 files changed, 61 insertions(+), 7 deletions(-)
> >
> > diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
> > index d02ae323996b..455cac7b2631 100644
> > --- a/kernel/bpf/helpers.c
> > +++ b/kernel/bpf/helpers.c
> > @@ -2939,6 +2939,31 @@ __bpf_kfunc void bpf_iter_bits_destroy(struct bpf_iter_bits *it)
> >       bpf_mem_free(&bpf_global_ma, kit->bits);
> >   }
> >
> > +/**
> > + * bpf_copy_from_user_str() - Copy a string from an unsafe user address
> > + * @dst:             Destination address, in kernel space.  This buffer must be at
> > + *                   least @dst__szk bytes long.
> > + * @dst__szk:        Maximum number of bytes to copy, including the trailing NUL.
> > + * @unsafe_ptr__ign: Source address, in user space.
> > + *
> > + * Copies a NUL-terminated string from userspace to BPF space. If user string is
> > + * too long this will still ensure zero termination in the dst buffer unless
> > + * buffer size is 0.
> > + */
> > +__bpf_kfunc int bpf_copy_from_user_str(void *dst, u32 dst__szk, const void __user *unsafe_ptr__ign)
> > +{
> > +     int ret;
> > +
> > +     if (unlikely(!dst__szk))
> > +             return 0;
> > +
> > +     ret = strncpy_from_user(dst, unsafe_ptr__ign, dst__szk);
>
> Does this function promise dst is null terminated if ret >= 0?
> It seems not to have null at the end if the source string is longer than
> dst_szk.
>
>

Good catch. I need to copy the same logic that exists in
`strncpy_from_user_nofault` which sets the last byte to '\0'.

> > +     if (unlikely(ret < 0))
> > +             memset(dst, 0, dst__szk);
> > +
> > +     return ret;
> > +}
> > +
> >   __bpf_kfunc_end_defs();
> >
> >   BTF_KFUNCS_START(generic_btf_ids)
> > @@ -3024,6 +3049,7 @@ BTF_ID_FLAGS(func, bpf_preempt_enable)
> >   BTF_ID_FLAGS(func, bpf_iter_bits_new, KF_ITER_NEW)
> >   BTF_ID_FLAGS(func, bpf_iter_bits_next, KF_ITER_NEXT | KF_RET_NULL)
> >   BTF_ID_FLAGS(func, bpf_iter_bits_destroy, KF_ITER_DESTROY)
> > +BTF_ID_FLAGS(func, bpf_copy_from_user_str, KF_SLEEPABLE)
> >   BTF_KFUNCS_END(common_btf_ids)
> >
> >   static const struct btf_kfunc_id_set common_kfunc_set = {
> > diff --git a/tools/testing/selftests/bpf/prog_tests/attach_probe.c b/tools/testing/selftests/bpf/prog_tests/attach_probe.c
> > index 7175af39134f..329c7862b52d 100644
> > --- a/tools/testing/selftests/bpf/prog_tests/attach_probe.c
> > +++ b/tools/testing/selftests/bpf/prog_tests/attach_probe.c
> > @@ -283,9 +283,11 @@ static void test_uprobe_sleepable(struct test_attach_probe *skel)
> >       trigger_func3();
> >
> >       ASSERT_EQ(skel->bss->uprobe_byname3_sleepable_res, 9, "check_uprobe_byname3_sleepable_res");
> > -     ASSERT_EQ(skel->bss->uprobe_byname3_res, 10, "check_uprobe_byname3_res");
> > -     ASSERT_EQ(skel->bss->uretprobe_byname3_sleepable_res, 11, "check_uretprobe_byname3_sleepable_res");
> > -     ASSERT_EQ(skel->bss->uretprobe_byname3_res, 12, "check_uretprobe_byname3_res");
> > +     ASSERT_EQ(skel->bss->uprobe_byname3_str_sleepable_res, 10, "check_uprobe_byname3_str_sleepable_res");
> > +     ASSERT_EQ(skel->bss->uprobe_byname3_res, 11, "check_uprobe_byname3_res");
> > +     ASSERT_EQ(skel->bss->uretprobe_byname3_sleepable_res, 12, "check_uretprobe_byname3_sleepable_res");
> > +     ASSERT_EQ(skel->bss->uretprobe_byname3_str_sleepable_res, 13, "check_uretprobe_byname3_str_sleepable_res");
> > +     ASSERT_EQ(skel->bss->uretprobe_byname3_res, 14, "check_uretprobe_byname3_res");
> >   }
> >
> >   void test_attach_probe(void)
> > diff --git a/tools/testing/selftests/bpf/prog_tests/read_vsyscall.c b/tools/testing/selftests/bpf/prog_tests/read_vsyscall.c
> > index 3405923fe4e6..c7b9ba8b1d06 100644
> > --- a/tools/testing/selftests/bpf/prog_tests/read_vsyscall.c
> > +++ b/tools/testing/selftests/bpf/prog_tests/read_vsyscall.c
> > @@ -23,6 +23,7 @@ struct read_ret_desc {
> >       { .name = "probe_read_user_str", .ret = -EFAULT },
> >       { .name = "copy_from_user", .ret = -EFAULT },
> >       { .name = "copy_from_user_task", .ret = -EFAULT },
> > +     { .name = "copy_from_user_str", .ret = -EFAULT },
> >   };
> >
> >   void test_read_vsyscall(void)
> > diff --git a/tools/testing/selftests/bpf/progs/read_vsyscall.c b/tools/testing/selftests/bpf/progs/read_vsyscall.c
> > index 986f96687ae1..27de1e907754 100644
> > --- a/tools/testing/selftests/bpf/progs/read_vsyscall.c
> > +++ b/tools/testing/selftests/bpf/progs/read_vsyscall.c
> > @@ -1,5 +1,6 @@
> >   // SPDX-License-Identifier: GPL-2.0
> >   /* Copyright (C) 2024. Huawei Technologies Co., Ltd */
> > +#include "vmlinux.h"
> >   #include <linux/types.h>
> >   #include <bpf/bpf_helpers.h>
> >
> > @@ -7,10 +8,15 @@
> >
> >   int target_pid = 0;
> >   void *user_ptr = 0;
> > -int read_ret[8];
> > +int read_ret[9];
> >
> >   char _license[] SEC("license") = "GPL";
> >
> > +/*
> > + * This is the only kfunc, the others are helpers
> > + */
> > +int bpf_copy_from_user_str(void *dst, u32, const void *) __weak __ksym;
> > +
> >   SEC("fentry/" SYS_PREFIX "sys_nanosleep")
> >   int do_probe_read(void *ctx)
> >   {
> > @@ -40,6 +46,7 @@ int do_copy_from_user(void *ctx)
> >       read_ret[6] = bpf_copy_from_user(buf, sizeof(buf), user_ptr);
> >       read_ret[7] = bpf_copy_from_user_task(buf, sizeof(buf), user_ptr,
> >                                             bpf_get_current_task_btf(), 0);
> > +     read_ret[8] = bpf_copy_from_user_str((char *)buf, sizeof(buf), user_ptr);
> >
> >       return 0;
> >   }
> > diff --git a/tools/testing/selftests/bpf/progs/test_attach_probe.c b/tools/testing/selftests/bpf/progs/test_attach_probe.c
> > index 68466a6ad18c..a90fa0bf103b 100644
> > --- a/tools/testing/selftests/bpf/progs/test_attach_probe.c
> > +++ b/tools/testing/selftests/bpf/progs/test_attach_probe.c
> > @@ -14,11 +14,15 @@ int uretprobe_byname_res = 0;
> >   int uprobe_byname2_res = 0;
> >   int uretprobe_byname2_res = 0;
> >   int uprobe_byname3_sleepable_res = 0;
> > +int uprobe_byname3_str_sleepable_res = 0;
> >   int uprobe_byname3_res = 0;
> >   int uretprobe_byname3_sleepable_res = 0;
> > +int uretprobe_byname3_str_sleepable_res = 0;
> >   int uretprobe_byname3_res = 0;
> >   void *user_ptr = 0;
> >
> > +int bpf_copy_from_user_str(void *dst, u32, const void *) __weak __ksym;
> > +
> >   SEC("ksyscall/nanosleep")
> >   int BPF_KSYSCALL(handle_kprobe_auto, struct __kernel_timespec *req, struct __kernel_timespec *rem)
> >   {
> > @@ -87,11 +91,23 @@ static __always_inline bool verify_sleepable_user_copy(void)
> >       return bpf_strncmp(data, sizeof(data), "test_data") == 0;
> >   }
> >
> > +static __always_inline bool verify_sleepable_user_copy_str(void)
> > +{
> > +     int ret;
> > +     char data[10];
> > +
> > +     ret = bpf_copy_from_user_str(data, sizeof(data), user_ptr);
> > +
> > +     return bpf_strncmp(data, sizeof(data), "test_data") == 0 && ret == 9;
> > +}
> > +
> >   SEC("uprobe.s//proc/self/exe:trigger_func3")
> >   int handle_uprobe_byname3_sleepable(struct pt_regs *ctx)
> >   {
> >       if (verify_sleepable_user_copy())
> >               uprobe_byname3_sleepable_res = 9;
> > +     if (verify_sleepable_user_copy_str())
> > +             uprobe_byname3_str_sleepable_res = 10;
> >       return 0;
> >   }
> >
> > @@ -102,7 +118,7 @@ int handle_uprobe_byname3_sleepable(struct pt_regs *ctx)
> >   SEC("uprobe//proc/self/exe:trigger_func3")
> >   int handle_uprobe_byname3(struct pt_regs *ctx)
> >   {
> > -     uprobe_byname3_res = 10;
> > +     uprobe_byname3_res = 11;
> >       return 0;
> >   }
> >
> > @@ -110,14 +126,16 @@ SEC("uretprobe.s//proc/self/exe:trigger_func3")
> >   int handle_uretprobe_byname3_sleepable(struct pt_regs *ctx)
> >   {
> >       if (verify_sleepable_user_copy())
> > -             uretprobe_byname3_sleepable_res = 11;
> > +             uretprobe_byname3_sleepable_res = 12;
> > +     if (verify_sleepable_user_copy_str())
> > +             uretprobe_byname3_str_sleepable_res = 13;
> >       return 0;
> >   }
> >
> >   SEC("uretprobe//proc/self/exe:trigger_func3")
> >   int handle_uretprobe_byname3(struct pt_regs *ctx)
> >   {
> > -     uretprobe_byname3_res = 12;
> > +     uretprobe_byname3_res = 14;
> >       return 0;
> >   }
> >
> > --
> > 2.44.1
> >
> >
diff mbox series

Patch

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index d02ae323996b..455cac7b2631 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -2939,6 +2939,31 @@  __bpf_kfunc void bpf_iter_bits_destroy(struct bpf_iter_bits *it)
 	bpf_mem_free(&bpf_global_ma, kit->bits);
 }

+/**
+ * bpf_copy_from_user_str() - Copy a string from an unsafe user address
+ * @dst:             Destination address, in kernel space.  This buffer must be at
+ *                   least @dst__szk bytes long.
+ * @dst__szk:        Maximum number of bytes to copy, including the trailing NUL.
+ * @unsafe_ptr__ign: Source address, in user space.
+ *
+ * Copies a NUL-terminated string from userspace to BPF space. If user string is
+ * too long this will still ensure zero termination in the dst buffer unless
+ * buffer size is 0.
+ */
+__bpf_kfunc int bpf_copy_from_user_str(void *dst, u32 dst__szk, const void __user *unsafe_ptr__ign)
+{
+	int ret;
+
+	if (unlikely(!dst__szk))
+		return 0;
+
+	ret = strncpy_from_user(dst, unsafe_ptr__ign, dst__szk);
+	if (unlikely(ret < 0))
+		memset(dst, 0, dst__szk);
+
+	return ret;
+}
+
 __bpf_kfunc_end_defs();

 BTF_KFUNCS_START(generic_btf_ids)
@@ -3024,6 +3049,7 @@  BTF_ID_FLAGS(func, bpf_preempt_enable)
 BTF_ID_FLAGS(func, bpf_iter_bits_new, KF_ITER_NEW)
 BTF_ID_FLAGS(func, bpf_iter_bits_next, KF_ITER_NEXT | KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_iter_bits_destroy, KF_ITER_DESTROY)
+BTF_ID_FLAGS(func, bpf_copy_from_user_str, KF_SLEEPABLE)
 BTF_KFUNCS_END(common_btf_ids)

 static const struct btf_kfunc_id_set common_kfunc_set = {
diff --git a/tools/testing/selftests/bpf/prog_tests/attach_probe.c b/tools/testing/selftests/bpf/prog_tests/attach_probe.c
index 7175af39134f..329c7862b52d 100644
--- a/tools/testing/selftests/bpf/prog_tests/attach_probe.c
+++ b/tools/testing/selftests/bpf/prog_tests/attach_probe.c
@@ -283,9 +283,11 @@  static void test_uprobe_sleepable(struct test_attach_probe *skel)
 	trigger_func3();

 	ASSERT_EQ(skel->bss->uprobe_byname3_sleepable_res, 9, "check_uprobe_byname3_sleepable_res");
-	ASSERT_EQ(skel->bss->uprobe_byname3_res, 10, "check_uprobe_byname3_res");
-	ASSERT_EQ(skel->bss->uretprobe_byname3_sleepable_res, 11, "check_uretprobe_byname3_sleepable_res");
-	ASSERT_EQ(skel->bss->uretprobe_byname3_res, 12, "check_uretprobe_byname3_res");
+	ASSERT_EQ(skel->bss->uprobe_byname3_str_sleepable_res, 10, "check_uprobe_byname3_str_sleepable_res");
+	ASSERT_EQ(skel->bss->uprobe_byname3_res, 11, "check_uprobe_byname3_res");
+	ASSERT_EQ(skel->bss->uretprobe_byname3_sleepable_res, 12, "check_uretprobe_byname3_sleepable_res");
+	ASSERT_EQ(skel->bss->uretprobe_byname3_str_sleepable_res, 13, "check_uretprobe_byname3_str_sleepable_res");
+	ASSERT_EQ(skel->bss->uretprobe_byname3_res, 14, "check_uretprobe_byname3_res");
 }

 void test_attach_probe(void)
diff --git a/tools/testing/selftests/bpf/prog_tests/read_vsyscall.c b/tools/testing/selftests/bpf/prog_tests/read_vsyscall.c
index 3405923fe4e6..c7b9ba8b1d06 100644
--- a/tools/testing/selftests/bpf/prog_tests/read_vsyscall.c
+++ b/tools/testing/selftests/bpf/prog_tests/read_vsyscall.c
@@ -23,6 +23,7 @@  struct read_ret_desc {
 	{ .name = "probe_read_user_str", .ret = -EFAULT },
 	{ .name = "copy_from_user", .ret = -EFAULT },
 	{ .name = "copy_from_user_task", .ret = -EFAULT },
+	{ .name = "copy_from_user_str", .ret = -EFAULT },
 };

 void test_read_vsyscall(void)
diff --git a/tools/testing/selftests/bpf/progs/read_vsyscall.c b/tools/testing/selftests/bpf/progs/read_vsyscall.c
index 986f96687ae1..27de1e907754 100644
--- a/tools/testing/selftests/bpf/progs/read_vsyscall.c
+++ b/tools/testing/selftests/bpf/progs/read_vsyscall.c
@@ -1,5 +1,6 @@ 
 // SPDX-License-Identifier: GPL-2.0
 /* Copyright (C) 2024. Huawei Technologies Co., Ltd */
+#include "vmlinux.h"
 #include <linux/types.h>
 #include <bpf/bpf_helpers.h>

@@ -7,10 +8,15 @@ 

 int target_pid = 0;
 void *user_ptr = 0;
-int read_ret[8];
+int read_ret[9];

 char _license[] SEC("license") = "GPL";

+/*
+ * This is the only kfunc, the others are helpers
+ */
+int bpf_copy_from_user_str(void *dst, u32, const void *) __weak __ksym;
+
 SEC("fentry/" SYS_PREFIX "sys_nanosleep")
 int do_probe_read(void *ctx)
 {
@@ -40,6 +46,7 @@  int do_copy_from_user(void *ctx)
 	read_ret[6] = bpf_copy_from_user(buf, sizeof(buf), user_ptr);
 	read_ret[7] = bpf_copy_from_user_task(buf, sizeof(buf), user_ptr,
 					      bpf_get_current_task_btf(), 0);
+	read_ret[8] = bpf_copy_from_user_str((char *)buf, sizeof(buf), user_ptr);

 	return 0;
 }
diff --git a/tools/testing/selftests/bpf/progs/test_attach_probe.c b/tools/testing/selftests/bpf/progs/test_attach_probe.c
index 68466a6ad18c..a90fa0bf103b 100644
--- a/tools/testing/selftests/bpf/progs/test_attach_probe.c
+++ b/tools/testing/selftests/bpf/progs/test_attach_probe.c
@@ -14,11 +14,15 @@  int uretprobe_byname_res = 0;
 int uprobe_byname2_res = 0;
 int uretprobe_byname2_res = 0;
 int uprobe_byname3_sleepable_res = 0;
+int uprobe_byname3_str_sleepable_res = 0;
 int uprobe_byname3_res = 0;
 int uretprobe_byname3_sleepable_res = 0;
+int uretprobe_byname3_str_sleepable_res = 0;
 int uretprobe_byname3_res = 0;
 void *user_ptr = 0;

+int bpf_copy_from_user_str(void *dst, u32, const void *) __weak __ksym;
+
 SEC("ksyscall/nanosleep")
 int BPF_KSYSCALL(handle_kprobe_auto, struct __kernel_timespec *req, struct __kernel_timespec *rem)
 {
@@ -87,11 +91,23 @@  static __always_inline bool verify_sleepable_user_copy(void)
 	return bpf_strncmp(data, sizeof(data), "test_data") == 0;
 }

+static __always_inline bool verify_sleepable_user_copy_str(void)
+{
+	int ret;
+	char data[10];
+
+	ret = bpf_copy_from_user_str(data, sizeof(data), user_ptr);
+
+	return bpf_strncmp(data, sizeof(data), "test_data") == 0 && ret == 9;
+}
+
 SEC("uprobe.s//proc/self/exe:trigger_func3")
 int handle_uprobe_byname3_sleepable(struct pt_regs *ctx)
 {
 	if (verify_sleepable_user_copy())
 		uprobe_byname3_sleepable_res = 9;
+	if (verify_sleepable_user_copy_str())
+		uprobe_byname3_str_sleepable_res = 10;
 	return 0;
 }

@@ -102,7 +118,7 @@  int handle_uprobe_byname3_sleepable(struct pt_regs *ctx)
 SEC("uprobe//proc/self/exe:trigger_func3")
 int handle_uprobe_byname3(struct pt_regs *ctx)
 {
-	uprobe_byname3_res = 10;
+	uprobe_byname3_res = 11;
 	return 0;
 }

@@ -110,14 +126,16 @@  SEC("uretprobe.s//proc/self/exe:trigger_func3")
 int handle_uretprobe_byname3_sleepable(struct pt_regs *ctx)
 {
 	if (verify_sleepable_user_copy())
-		uretprobe_byname3_sleepable_res = 11;
+		uretprobe_byname3_sleepable_res = 12;
+	if (verify_sleepable_user_copy_str())
+		uretprobe_byname3_str_sleepable_res = 13;
 	return 0;
 }

 SEC("uretprobe//proc/self/exe:trigger_func3")
 int handle_uretprobe_byname3(struct pt_regs *ctx)
 {
-	uretprobe_byname3_res = 12;
+	uretprobe_byname3_res = 14;
 	return 0;
 }