| Message ID | YnJNTIJeB2NHK9Jh@localhost.localdomain (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] module: fix [e_shstrndx].sh_size=0 OOB access | expand |
On Wed, May 04, 2022 at 12:54:20PM +0300, Alexey Dobriyan wrote: > It is trivial to craft a module to trigger OOB access in this line: > > if (info->secstrings[strhdr->sh_size - 1] != '\0') { > > BUG: unable to handle page fault for address: ffffc90000aa0fff > #PF: supervisor read access in kernel mode > #PF: error_code(0x0000) - not-present page > PGD 100000067 P4D 100000067 PUD 100066067 PMD 10436f067 PTE 0 > Oops: 0000 [#1] PREEMPT SMP PTI > CPU: 7 PID: 1215 Comm: insmod Not tainted 5.18.0-rc5-00007-g9bf578647087-dirty #10 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-4.fc34 04/01/2014 > RIP: 0010:load_module+0x19b/0x2391 > > Fixes: ec2a29593c83 ("module: harden ELF info handling") > Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> Thanks! I rebased your patch onto modules-next [0] and applied onto modules-testing and pushed out there. If that doesn't break I'll then push to modules-next as well. Luis
--- a/kernel/module.c +++ b/kernel/module.c @@ -3033,6 +3033,10 @@ static int elf_validity_check(struct load_info *info) * strings in the section safe. */ info->secstrings = (void *)info->hdr + strhdr->sh_offset; + if (strhdr->sh_size == 0) { + pr_err("empty section name table\n"); + goto no_exec; + } if (info->secstrings[strhdr->sh_size - 1] != '\0') { pr_err("ELF Spec violation: section name table isn't null terminated\n"); goto no_exec; Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> --- kernel/module.c | 4 ++++ 1 file changed, 4 insertions(+) --- a/kernel/module.c +++ b/kernel/module.c @@ -3033,6 +3033,10 @@ static int elf_validity_check(struct load_info *info) * strings in the section safe. */ info->secstrings = (void *)info->hdr + strhdr->sh_offset; + if (strhdr->sh_size == 0) { + pr_err("empty section name table\n"); + goto no_exec; + } if (info->secstrings[strhdr->sh_size - 1] != '\0') { pr_err("ELF Spec violation: section name table isn't null terminated\n"); goto no_exec;
It is trivial to craft a module to trigger OOB access in this line: if (info->secstrings[strhdr->sh_size - 1] != '\0') { BUG: unable to handle page fault for address: ffffc90000aa0fff #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 100000067 P4D 100000067 PUD 100066067 PMD 10436f067 PTE 0 Oops: 0000 [#1] PREEMPT SMP PTI CPU: 7 PID: 1215 Comm: insmod Not tainted 5.18.0-rc5-00007-g9bf578647087-dirty #10 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-4.fc34 04/01/2014 RIP: 0010:load_module+0x19b/0x2391 Fixes: ec2a29593c83 ("module: harden ELF info handling") Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> --- kernel/module.c | 4 ++++ 1 file changed, 4 insertions(+)