linux-kernel - [PATCH 1/3] binfmt_elf_fdpic: fix AUXV size calculation for ELF_HWCAP3 and ELF

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Message-ID: <20260108050748.520792-2-avagin@google.com>
Date: Thu,  8 Jan 2026 05:07:46 +0000
From: Andrei Vagin <avagin@...gle.com>
To: Kees Cook <kees@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org, 
	linux-mm@...ck.org, criu@...ts.linux.dev, 
	Andrew Morton <akpm@...ux-foundation.org>, Chen Ridong <chenridong@...wei.com>, 
	Christian Brauner <brauner@...nel.org>, David Hildenbrand <david@...nel.org>, 
	Eric Biederman <ebiederm@...ssion.com>, Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, 
	Michal Koutny <mkoutny@...e.com>, Andrei Vagin <avagin@...gle.com>, Mark Brown <broonie@...nel.org>, 
	Max Filippov <jcmvbkbc@...il.com>
Subject: [PATCH 1/3] binfmt_elf_fdpic: fix AUXV size calculation for
 ELF_HWCAP3 and ELF_HWCAP4

Commit 4e6e8c2b757f ("binfmt_elf: Wire up AT_HWCAP3 at AT_HWCAP4") added
support for AT_HWCAP3 and AT_HWCAP4, but it missed updating the AUX
vector size calculation in create_elf_fdpic_tables() and
AT_VECTOR_SIZE_BASE in include/linux/auxvec.h.

Similar to the fix for ELF_HWCAP2 in commit c6a09e342f8e
("binfmt_elf_fdpic: fix AUXV size calculation when ELF_HWCAP2 is defined"),
this omission leads to a mismatch between the reserved space and the
actual number of AUX entries, eventually triggering a kernel BUG_ON(csp != sp).

Fix this by incrementing nitems when ELF_HWCAP3 or ELF_HWCAP4 are defined
and updating AT_VECTOR_SIZE_BASE.

Cc: Mark Brown <broonie@...nel.org>
Cc: Max Filippov <jcmvbkbc@...il.com>
Fixes: 4e6e8c2b757f ("binfmt_elf: Wire up AT_HWCAP3 at AT_HWCAP4")
Signed-off-by: Andrei Vagin <avagin@...gle.com>
---
 fs/binfmt_elf_fdpic.c  | 6 ++++++
 include/linux/auxvec.h | 2 +-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
index 48fd2de3bca0..a3d4e6973b29 100644
--- a/fs/binfmt_elf_fdpic.c
+++ b/fs/binfmt_elf_fdpic.c
@@ -595,6 +595,12 @@ static int create_elf_fdpic_tables(struct linux_binprm *bprm,
 #ifdef ELF_HWCAP2
 	nitems++;
 #endif
+#ifdef ELF_HWCAP3
+	nitems++;
+#endif
+#ifdef ELF_HWCAP4
+	nitems++;
+#endif
 
 	csp = sp;
 	sp -= nitems * 2 * sizeof(unsigned long);
diff --git a/include/linux/auxvec.h b/include/linux/auxvec.h
index 407f7005e6d6..8bcb9b726262 100644
--- a/include/linux/auxvec.h
+++ b/include/linux/auxvec.h
@@ -4,6 +4,6 @@
 
 #include <uapi/linux/auxvec.h>
 
-#define AT_VECTOR_SIZE_BASE 22 /* NEW_AUX_ENT entries in auxiliary table */
+#define AT_VECTOR_SIZE_BASE 24 /* NEW_AUX_ENT entries in auxiliary table */
   /* number of "#define AT_.*" above, minus {AT_NULL, AT_IGNORE, AT_NOTELF} */
 #endif /* _LINUX_AUXVEC_H */
-- 
2.52.0.351.gbe84eed79e-goog