Date: Mon, 29 Apr 2024 02:49:28 GMT From: Olivier Certner <olce@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-branches@FreeBSD.org Subject: git: 3e4989127020 - stable/14 - sys_procctl(): Make it clear that negative commands are invalid Message-ID: <202404290249.43T2nSsM073439@gitrepo.freebsd.org>
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The branch stable/14 has been updated by olce: URL: https://cgit.FreeBSD.org/src/commit/?id=3e498912702094b35f61fd86e557c4f4148aead8 commit 3e498912702094b35f61fd86e557c4f4148aead8 Author: Olivier Certner <olce@FreeBSD.org> AuthorDate: 2024-04-10 14:32:32 +0000 Commit: Olivier Certner <olce@FreeBSD.org> CommitDate: 2024-04-29 02:48:02 +0000 sys_procctl(): Make it clear that negative commands are invalid An initial reading of the preamble of sys_procctl() gives the impression that no test prevents a malicious user from passing a negative commands index (in 'uap->com'), which is soon used as an index into the static array procctl_cmds_info[]. However, a closer examination leads to the conclusion that the existing code is technically correct. Indeed, the comparison of 'uap->com' to the nitems() expression, which expands to a ratio of sizeof(), leads to a conversion of 'uap->com' to an 'unsigned int' as per Usual Arithmetic Conversions/Integer Promotions applied by '<=', because sizeof() returns 'size_t' values, and we define 'size_t' as an equivalent of 'unsigned int' (which is not mandated by the standard, the latter allowing, e.g., integers of lower ranks). With this conversion, negative values of 'uap->com' are automatically ruled-out since they are converted to very big unsigned integers which are caught by the test. An analysis of assembly code produced by LLVM 16 on amd64 and practical tests confirm that no exploitation is possible. However, the guard code as written is misleading to readers and might trip up static analysis tools. Make sure that negative values are explicitly excluded so that it is immediately clear that EINVAL will be returned in this case. Build tested with clang 16 and GCC 12. Approved by: markj (mentor) MFC after: 1 week Sponsored by: The FreeBSD Foundation (cherry picked from commit afc10f8bba3dd293a66461aaca41237c986b6ca7) Approved by: emaste (mentor) --- sys/kern/kern_procctl.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/sys/kern/kern_procctl.c b/sys/kern/kern_procctl.c index e6a142b2a7ac..9e860e7c80a5 100644 --- a/sys/kern/kern_procctl.c +++ b/sys/kern/kern_procctl.c @@ -1123,7 +1123,7 @@ sys_procctl(struct thread *td, struct procctl_args *uap) if (uap->com >= PROC_PROCCTL_MD_MIN) return (cpu_procctl(td, uap->idtype, uap->id, uap->com, uap->data)); - if (uap->com == 0 || uap->com >= nitems(procctl_cmds_info)) + if (uap->com <= 0 || uap->com >= nitems(procctl_cmds_info)) return (EINVAL); cmd_info = &procctl_cmds_info[uap->com]; bzero(&x, sizeof(x));
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