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Message-ID: <20260421123411.GM1827@brightrain.aerifal.cx>
Date: Tue, 21 Apr 2026 08:34:11 -0400
From: Rich Felker <dalias@...c.org>
To: Florian Schmaus <florian.schmaus@...asip.com>
Cc: musl@...ts.openwall.com
Subject: Re: [PATCH] dynlink: set errno in case mprotect() fails
On Tue, Apr 21, 2026 at 09:57:27AM +0200, Florian Schmaus wrote:
> The format string of the error message uses %m to print the value of
> errno in human-readable form. But the low-level __syscall() macro,
> used to invoke mprotect(), will not implicitly set errno. Fix this by
> setting errno explicitly before emitting the error message.
> ---
> ldso/dynlink.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/ldso/dynlink.c b/ldso/dynlink.c
> index 715948f4f8b3..db0f9f52461c 100644
> --- a/ldso/dynlink.c
> +++ b/ldso/dynlink.c
> @@ -1424,6 +1424,7 @@ static void reloc_all(struct dso *p)
> long ret = __syscall(SYS_mprotect, laddr(p, p->relro_start),
> p->relro_end-p->relro_start, PROT_READ);
> if (ret != 0 && ret != -ENOSYS) {
> + errno = -ret;
> error("Error relocating %s: RELRO protection failed: %m",
> p->name);
> if (runtime) longjmp(*rtld_fail, 1);
> --
> 2.53.0
I think this requires further analysis. See commit
63c67053a3e42e9dff788de432f82ff07d4d772a. Avoiding accessing errno was
intentional here, and the access buried in the error path is probably
a bug. But we need to look back at the constraints to determine how to
fix it right.
Rich
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