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b13448dd64
Function bpf_patch_insn_data() has the following structure:
static struct bpf_prog *bpf_patch_insn_data(... env ...)
{
struct bpf_prog *new_prog;
struct bpf_insn_aux_data *new_data = NULL;
if (len > 1) {
new_data = vrealloc(...); // <--------- (1)
if (!new_data)
return NULL;
env->insn_aux_data = new_data; // <---- (2)
}
new_prog = bpf_patch_insn_single(env->prog, off, patch, len);
if (IS_ERR(new_prog)) {
...
vfree(new_data); // <----------------- (3)
return NULL;
}
... happy path ...
}
In case if bpf_patch_insn_single() returns an error the `new_data`
allocated at (1) will be freed at (3). However, at (2) this pointer
is stored in `env->insn_aux_data`. Which is freed unconditionally
by verifier.c:bpf_check() on both happy and error paths.
Thus, leading to double-free.
Fix this by removing vfree() call at (3), ownership over `new_data` is
already passed to `env->insn_aux_data` at this point.
Fixes: 77620d1267 ("bpf: use realloc in bpf_patch_insn_data")
Reported-by: Chris Mason <clm@meta.com>
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20250912-patch-insn-data-double-free-v1-1-af05bd85a21a@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.