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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id y197-20020a62cece000000b0056c47a5c34dsm662595pfg.122.2022.11.10.21.57.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 10 Nov 2022 21:57:57 -0800 (PST) From: Kees Cook To: Pedro Falcato Cc: Kees Cook , Rich Felker , Fangrui Song , Alexander Viro , Eric Biederman , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: [PATCH] binfmt_elf: Allow .bss in any interp PT_LOAD Date: Thu, 10 Nov 2022 21:57:54 -0800 Message-Id: <20221111055747.never.202-kees@kernel.org> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=1993; h=from:subject:message-id; bh=IFv7zG9ua/TUw6RPzUQWoXA14J5yfz12EiQFTB5lii0=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBjbeRibkBnJb+JHCktBamRZlj///oiFFeK7VpOpPsB 44aQDc2JAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCY23kYgAKCRCJcvTf3G3AJnJvD/ wMpSquxigcVJfg5ewqR3cpfP5urArMS1hWUeQchcdyXTMfEUFgqyt9Ty+7OE6vdD/z3R3uiC3lpphP FBxBvEkLF5ZynousHcyUauCkIiwZT1PLigA2z5DGCbu2tRUOeUZEI4uaYvMxWwJf+LoEIgjeWcXlHH QfBmP/w18M2HZvcH5ma39HbdZQPEU9Nn1sa4/WuZLf6xs+a6yVjJL2JpWk1Z6Md0kGbSu/n7KQkvRM OtJvFB3QrDrI8Mhm/UgZ/44bBI8kpStf/wXcD2PCGfSie6D+bPUvNlMk0t8eVQ0tq22d3po13Shtph N8IJDsgmVLbS0jbJLbWS5DQN5RlRrvmd+ss6JeZeCxMQVyJsUbft/Yydnvd6uxj/WLMK/Y1SsMrBgR vvBEdrAbJ1uO6PTohfPWyTOBG4P0nwz5/GodjBItoS6ceZjbf5tr82KhuQ8skBW+uztDUbi98znHu7 494BhsMzVXPETrqKnMIshOd0fSUYuawrnNvCqKGN0O4MYRiv06uCFYyyK45PqZOsFT2NA7U1hC8FF+ 11Hn4IoGq6LaAsuVbgTfBE7LR0lxPnBLwXLrsf3woKx8wRL7SCI7XKcYsaHeu0JFg/ukPkU1tMpiII tv6vNwpD91PO6uTpbXuWBE8xgYj3IBtoPba44NCzuwf246ajS31oQK2S+zVA== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org Traditionally, only the final PT_LOAD for load_elf_interp() supported having p_memsz > p_filesz. Recently, lld's construction of musl's libc.so on PowerPC64 started having two PT_LOAD program headers with p_memsz > p_filesz. As the least invasive change possible, check for p_memsz > p_filesz for each PT_LOAD in load_elf_interp. Reported-by: Rich Felker Link: https://maskray.me/blog/2022-11-05-lld-musl-powerpc64 Cc: Pedro Falcato Cc: Fangrui Song Cc: Alexander Viro Cc: Eric Biederman Cc: linux-fsdevel@vger.kernel.org Cc: linux-mm@kvack.org Signed-off-by: Kees Cook --- Rich, Pedro, and Fangrui, are you able to test this change? I haven't constructed a trivial reproducer yet (though it would be nice to have a self-contained test-case). --- fs/binfmt_elf.c | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-) diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index 528e2ac8931f..3f07945ff085 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -673,18 +673,19 @@ static unsigned long load_elf_interp(struct elfhdr *interp_elf_ex, last_bss = k; bss_prot = elf_prot; } + + /* + * Now fill out any zeroed region (e.g. .bss): first pad the + * last page from the file up to the page boundary, and zero + * it from elf_bss up to the end of the page. + */ + if (last_bss > elf_bss && padzero(elf_bss)) { + error = -EFAULT; + goto out; + } } } - /* - * Now fill out the bss section: first pad the last page from - * the file up to the page boundary, and zero it from elf_bss - * up to the end of the page. - */ - if (padzero(elf_bss)) { - error = -EFAULT; - goto out; - } /* * Next, align both the file and mem bss up to the page size, * since this is where elf_bss was just zeroed up to, and where