linux-kernel - [PATCH] binfmt_elf: dynamically allocate note.data in parse_elf

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Date:   Wed,  7 Jun 2023 16:42:27 +0200
From:   Christian Marangi <ansuelsmth@...il.com>
To:     Alexander Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <brauner@...nel.org>,
        Eric Biederman <ebiederm@...ssion.com>,
        Kees Cook <keescook@...omium.org>,
        Mark Brown <broonie@...nel.org>,
        Dave Martin <Dave.Martin@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Cc:     Christian Marangi <ansuelsmth@...il.com>, stable@...r.kernel.org
Subject: [PATCH] binfmt_elf: dynamically allocate note.data in parse_elf_properties

Dynamically allocate note.data in parse_elf_properties to fix
compilation warning on some arch.

On some arch note.data exceed the stack limit for a single function and
this cause the following compilation warning:
fs/binfmt_elf.c: In function 'parse_elf_properties.isra':
fs/binfmt_elf.c:821:1: error: the frame size of 1040 bytes is larger than 1024 bytes [-Werror=frame-larger-than=]
  821 | }
      | ^
cc1: all warnings being treated as errors

Fix this by dynamically allocating the array.
Update the sizeof of the union to the biggest element allocated.

Fixes: 00e19ceec80b ("ELF: Add ELF program property parsing support")
Signed-off-by: Christian Marangi <ansuelsmth@...il.com>
Cc: stable@...r.kernel.org # v5.8+
---
 fs/binfmt_elf.c | 36 +++++++++++++++++++++++++-----------
 1 file changed, 25 insertions(+), 11 deletions(-)

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 44b4c42ab8e8..90daa623ca13 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -768,7 +768,7 @@ static int parse_elf_properties(struct file *f, const struct elf_phdr *phdr,
 {
 	union {
 		struct elf_note nhdr;
-		char data[NOTE_DATA_SZ];
+		char *data;
 	} note;
 	loff_t pos;
 	ssize_t n;
@@ -785,29 +785,41 @@ static int parse_elf_properties(struct file *f, const struct elf_phdr *phdr,
 		return -ENOEXEC;
 
 	/* If the properties are crazy large, that's too bad (for now): */
-	if (phdr->p_filesz > sizeof(note))
+	if (phdr->p_filesz > sizeof(*note.data) * NOTE_DATA_SZ)
 		return -ENOEXEC;
 
+	note.data = kcalloc(NOTE_DATA_SZ, sizeof(*note.data), GFP_KERNEL);
+	if (!note.data)
+		return -ENOMEM;
+
 	pos = phdr->p_offset;
 	n = kernel_read(f, &note, phdr->p_filesz, &pos);
 
-	BUILD_BUG_ON(sizeof(note) < sizeof(note.nhdr) + NOTE_NAME_SZ);
-	if (n < 0 || n < sizeof(note.nhdr) + NOTE_NAME_SZ)
-		return -EIO;
+	BUILD_BUG_ON(sizeof(*note.data) * NOTE_DATA_SZ < sizeof(note.nhdr) + NOTE_NAME_SZ);
+	if (n < 0 || n < sizeof(note.nhdr) + NOTE_NAME_SZ) {
+		ret = -EIO;
+		goto exit;
+	}
 
 	if (note.nhdr.n_type != NT_GNU_PROPERTY_TYPE_0 ||
 	    note.nhdr.n_namesz != NOTE_NAME_SZ ||
 	    strncmp(note.data + sizeof(note.nhdr),
-		    GNU_PROPERTY_TYPE_0_NAME, n - sizeof(note.nhdr)))
-		return -ENOEXEC;
+		    GNU_PROPERTY_TYPE_0_NAME, n - sizeof(note.nhdr))) {
+		ret = -ENOEXEC;
+		goto exit;
+	}
 
 	off = round_up(sizeof(note.nhdr) + NOTE_NAME_SZ,
 		       ELF_GNU_PROPERTY_ALIGN);
-	if (off > n)
-		return -ENOEXEC;
+	if (off > n) {
+		ret = -ENOEXEC;
+		goto exit;
+	}
 
-	if (note.nhdr.n_descsz > n - off)
-		return -ENOEXEC;
+	if (note.nhdr.n_descsz > n - off) {
+		ret = -ENOEXEC;
+		goto exit;
+	}
 	datasz = off + note.nhdr.n_descsz;
 
 	have_prev_type = false;
@@ -817,6 +829,8 @@ static int parse_elf_properties(struct file *f, const struct elf_phdr *phdr,
 		have_prev_type = true;
 	} while (!ret);
 
+exit:
+	kfree(note.data);
 	return ret == -ENOENT ? 0 : ret;
 }
 
-- 
2.39.2