[DTrace-devel] [PATCH] usdt: enforce provider name size limit

[Eugene Loh]

I'd like to understand this patch better.  In particular, in what sense 
can a PID take up to 10 chars?  What if it isn't that wide? If by 
coincidence all my PIDs just happen to be narrower, why must my provider 
name make space for a PID I'll never see.  IIUC, a PID will "typically" 
(whatever that means) not exceed 32768, well, or maybe 4194304.  So I 
might even be guaranteed that my PIDs will be shorter than 10 chars.

On 2/17/26 11:35, Kris Van Hees via DTrace-devel wrote:
> Since USDT provider names have a PID appended to them, the base provider
> name cannot be longer than 53 characters (PID can take up to 10 chars).
>
> Signed-off-by: Kris Van Hees <kris.van.hees at oracle.com>
> ---
>   libdtrace/dt_link.c                     | 24 ++++++++++++---
>   test/unittest/usdt/err.prov-too-long.r  |  3 ++
>   test/unittest/usdt/err.prov-too-long.sh | 41 +++++++++++++++++++++++++
>   3 files changed, 63 insertions(+), 5 deletions(-)
>   create mode 100644 test/unittest/usdt/err.prov-too-long.r
>   create mode 100755 test/unittest/usdt/err.prov-too-long.sh
>
> diff --git a/libdtrace/dt_link.c b/libdtrace/dt_link.c
> index ffa16d9a..e77f06f7 100644
> --- a/libdtrace/dt_link.c
> +++ b/libdtrace/dt_link.c
> @@ -148,7 +148,15 @@ note_add_provider(usdt_elf_t *usdt, dt_provider_t *pvp)
>   	usdt->base = ALIGN(usdt->base + usdt->size, 4);
>   	usdt->size = 0;
>   
> +	/* Ensure there is enough space in the provider name for the PID. */
>   	len = strlen(pvp->desc.dtvd_name);
> +	if (len > DTRACE_PROVNAMELEN - 10 - 1)
> +		return dt_link_error(usdt->dtp, NULL, -1,
> +				     "USDT provider name may not exceed %d "
> +				     "characters: %s\n",
> +				     DTRACE_PROVNAMELEN - 11,
> +				     pvp->desc.dtvd_name);
> +
>   	sz = PROV_NOTE_HEADSZ +
>   	     ALIGN(len + 1, 4) +	/* provider name */
>   	     6 * sizeof(uint32_t);	/* stability attributes */
> @@ -382,12 +390,16 @@ create_elf64(dtrace_hdl_t *dtp, dtrace_prog_t *pgp, int fd, uint_t flags)
>   	shdr->sh_addralign = sizeof(char);
>   
>   	/* Add the provider definitions. */
> -	while ((pvp = dt_htab_next(dtp->dt_provs, &it)) != NULL)
> -		note_add_provider(usdt, pvp);
> +	while ((pvp = dt_htab_next(dtp->dt_provs, &it)) != NULL) {
> +		if (note_add_provider(usdt, pvp) == -1)
> +			goto fail;
> +	}
>   
>   	if (!(flags & DTRACE_D_STRIP)) {
> -		note_add_version(usdt);
> -		note_add_utsname(usdt);
> +		if (note_add_version(usdt) == -1)
> +			goto fail;
> +		if (note_add_utsname(usdt) == -1)
> +			goto fail;
>   	}
>   
>   	dt_free(dtp, usdt);
> @@ -492,7 +504,9 @@ dtrace_program_link(dtrace_hdl_t *dtp, dtrace_prog_t *pgp, uint_t dflags,
>   	if (!dtp->dt_lazyload)
>   		unlink(file);
>   
> -	create_elf64(dtp, pgp, fd, dflags | dtp->dt_dflags);
> +	ret = create_elf64(dtp, pgp, fd, dflags | dtp->dt_dflags);
> +	if (ret == -1)
> +		goto done;
>   
>   	if (status != 0 || lseek(fd, 0, SEEK_SET) != 0)
>   		return dt_link_error(dtp, NULL, -1,
> diff --git a/test/unittest/usdt/err.prov-too-long.r b/test/unittest/usdt/err.prov-too-long.r
> new file mode 100644
> index 00000000..1305f434
> --- /dev/null
> +++ b/test/unittest/usdt/err.prov-too-long.r
> @@ -0,0 +1,3 @@
> +-- @@stderr --
> +dtrace: failed to link script prov: USDT provider name may not exceed 53 characters: test_12345678901234567890123456789012345678901234_prov
> +failed to create DOF
> diff --git a/test/unittest/usdt/err.prov-too-long.sh b/test/unittest/usdt/err.prov-too-long.sh
> new file mode 100755
> index 00000000..599e461e
> --- /dev/null
> +++ b/test/unittest/usdt/err.prov-too-long.sh
> @@ -0,0 +1,41 @@
> +#!/bin/bash
> +#
> +# Oracle Linux DTrace.
> +# Copyright (c) 2026, Oracle and/or its affiliates. All rights reserved.
> +# Licensed under the Universal Permissive License v 1.0 as shown at
> +# http://oss.oracle.com/licenses/upl.
> +#
> +
> +# Ensure that provider names longer than 53 chars are rejected at link time.
> +
> +if [ $# != 1 ]; then
> +	echo expected one argument: '<'dtrace-path'>'
> +	exit 2
> +fi
> +
> +
> +dtrace=$1
> +
> +DIRNAME="$tmpdir/prov-too-long.$$.$RANDOM"
> +mkdir -p $DIRNAME
> +cd $DIRNAME
> +
> +cat > prov.d <<EOF
> +/* Provider name is 53 chars long */
> +provider test_1234567890123456789012345678901234567890123_prov {
> +	probe go();
> +};
> +/* Provider name is 54 chars long */
> +provider test_12345678901234567890123456789012345678901234_prov {
> +	probe go();
> +};
> +EOF
> +
> +$dtrace $dt_flags -G -s prov.d
> +if [ $? -ne 0 ]; then
> +	echo "failed to create DOF" >& 2
> +	exit 1
> +fi
> +
> +echo "DOF creation should have failed" >& 2
> +exit 0