[PATCH RESEND 0/3] x86/vdso: Improve vdso=/vdso32= boot parameter validation

[PATCH RESEND 0/3] x86/vdso: Improve vdso=/vdso32= boot parameter validation

[Thorsten Blum]

Replace the deprecated simple_strtoul() [1] with kstrtouint() when
parsing the vDSO boot parameters. This provides strict input validation,
rejects partial input, and warns when disabling vDSO for invalid values.

Adjust both warnings for consistency and update the documentation.

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#simple-strtol-simple-strtoll-simple-strtoul-simple-strtoull

Thorsten Blum (3):
  x86/vdso: Use kstrtouint() to validate vdso= boot parameter
  x86/vdso: Use kstrtouint() to validate vdso32= boot parameter
  Documentation/arch/x86: Remove obsolete vdso32=2 compatibility note

 Documentation/admin-guide/kernel-parameters.txt |  5 +----
 arch/x86/entry/vdso/vdso32-setup.c              | 10 ++++------
 arch/x86/entry/vdso/vma.c                       |  6 +++++-
 3 files changed, 10 insertions(+), 11 deletions(-)


base-commit: 979c294509f9248fe1e7c358d582fb37dd5ca12d

[PATCH RESEND 1/3] x86/vdso: Use kstrtouint() to validate vdso= boot parameter

[Thorsten Blum]

Replace the deprecated simple_strtoul() with kstrtouint() when parsing
the vdso= boot parameter.

simple_strtoul() accepts partial input and silently converts invalid
input to 0. Use kstrtouint() for strict input validation instead and
reject malformed input. Accept only 0 and 1; warn and disable vDSO
support otherwise.

kstrtouint() converts the input string directly to an unsigned int,
avoiding an implicit conversion when assigning to vdso64_enabled.

Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
---
 arch/x86/entry/vdso/vma.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
index 18dfd80a81ef..c5c09c28388e 100644
--- a/arch/x86/entry/vdso/vma.c
+++ b/arch/x86/entry/vdso/vma.c
@@ -299,7 +299,11 @@ bool arch_syscall_is_vdso_sigreturn(struct pt_regs *regs)
 #ifdef CONFIG_X86_64
 static __init int vdso_setup(char *s)
 {
-	vdso64_enabled = simple_strtoul(s, NULL, 0);
+	if (kstrtouint(s, 0, &vdso64_enabled) || vdso64_enabled > 1) {
+		pr_warn("vdso= values other than 0 and 1 are invalid; vdso disabled\n");
+		vdso64_enabled = 0;
+	}
+
 	return 1;
 }
 __setup("vdso=", vdso_setup);

[PATCH RESEND 2/3] x86/vdso: Use kstrtouint() to validate vdso32= boot parameter

[Thorsten Blum]

Replace the deprecated simple_strtoul() with kstrtouint() when parsing
the vdso32= boot parameter and its X86_32 vdso= alias.

simple_strtoul() accepts partial input and silently converts invalid
input to 0. Use kstrtouint() for strict input validation instead and
reject malformed input. Accept only 0 and 1; warn and disable vDSO
support otherwise.

kstrtouint() converts the input string directly to an unsigned int,
avoiding an implicit conversion when assigning to vdso32_enabled.

Update the vdso32= handler comment to reflect the supported values.

Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
---
 arch/x86/entry/vdso/vdso32-setup.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/arch/x86/entry/vdso/vdso32-setup.c b/arch/x86/entry/vdso/vdso32-setup.c
index 8894013eea1d..5f3e548ebf19 100644
--- a/arch/x86/entry/vdso/vdso32-setup.c
+++ b/arch/x86/entry/vdso/vdso32-setup.c
@@ -30,10 +30,8 @@ unsigned int __read_mostly vdso32_enabled = VDSO_DEFAULT;
 
 static int __init vdso32_setup(char *s)
 {
-	vdso32_enabled = simple_strtoul(s, NULL, 0);
-
-	if (vdso32_enabled > 1) {
-		pr_warn("vdso32 values other than 0 and 1 are no longer allowed; vdso disabled\n");
+	if (kstrtouint(s, 0, &vdso32_enabled) || vdso32_enabled > 1) {
+		pr_warn("vdso32= values other than 0 and 1 are invalid; vdso disabled\n");
 		vdso32_enabled = 0;
 	}
 
@@ -41,9 +39,9 @@ static int __init vdso32_setup(char *s)
 }
 
 /*
- * For consistency, the argument vdso32=[012] affects the 32-bit vDSO
+ * For consistency, the argument vdso32=[01] affects the 32-bit vDSO
  * behavior on both 64-bit and 32-bit kernels.
- * On 32-bit kernels, vdso=[012] means the same thing.
+ * On 32-bit kernels, vdso=[01] means the same thing.
  */
 __setup("vdso32=", vdso32_setup);
 

[PATCH RESEND 3/3] Documentation/arch/x86: Remove obsolete vdso32=2 compatibility note

[Thorsten Blum]

Commit b0b49f2673f0 ("x86, vdso: Remove compat vdso support") removed
compat vDSO support and documented vdso32=2 as an alias for vdso32=0.

However, since commit c06989da39cd ("x86/vdso: Ensure vdso32_enabled
gets set to valid values only"), vdso32_setup() accepts only 0 and 1.

Remove the obsolete vdso32=2 compatibility note and document only the
supported values.

Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
---
 Documentation/admin-guide/kernel-parameters.txt | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index b5493a7f8f22..8a55ec37d066 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -8260,15 +8260,12 @@ Kernel parameters
 
 	vdso32=		[X86] Control the 32-bit vDSO
 			vdso32=1: enable 32-bit VDSO
-			vdso32=0 or vdso32=2: disable 32-bit VDSO
+			vdso32=0: disable 32-bit VDSO
 
 			See the help text for CONFIG_COMPAT_VDSO for more
 			details.  If CONFIG_COMPAT_VDSO is set, the default is
 			vdso32=0; otherwise, the default is vdso32=1.
 
-			For compatibility with older kernels, vdso32=2 is an
-			alias for vdso32=0.
-
 			Try vdso32=0 if you encounter an error that says:
 			dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
 

Re: [PATCH RESEND 0/3] x86/vdso: Improve vdso=/vdso32= boot parameter validation

[Dave Hansen]

On 7/13/26 16:34, Thorsten Blum wrote:
> Replace the deprecated simple_strtoul() [1] with kstrtouint() when
> parsing the vDSO boot parameters. This provides strict input validation,
> rejects partial input, and warns when disabling vDSO for invalid values.

Hey Thorsten,

I'm curious what motivated this change. Were you trying to manipulate
the VDSO and ran into some difficulties? Or is it a larger effort to
audit and simple_strtoul() users?

Re: [PATCH RESEND 0/3] x86/vdso: Improve vdso=/vdso32= boot parameter validation

[Thorsten Blum]

On Mon, Jul 13, 2026 at 04:40:55PM -0700, Dave Hansen wrote:
> On 7/13/26 16:34, Thorsten Blum wrote:
> > Replace the deprecated simple_strtoul() [1] with kstrtouint() when
> > parsing the vDSO boot parameters. This provides strict input validation,
> > rejects partial input, and warns when disabling vDSO for invalid values.
> 
> Hey Thorsten,
> 
> I'm curious what motivated this change. Were you trying to manipulate
> the VDSO and ran into some difficulties? Or is it a larger effort to
> audit and simple_strtoul() users?

I just stumbled upon it while studying the code, and simple_strto*()
calls are often an opportunity to improve input validation.