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binfmt_elf_fdpic: fix /proc/<pid>/auxv

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Althought FDPIC linux kernel provides /proc/<pid>/auxv files they are
empty because there's no code that initializes mm->saved_auxv in the
FDPIC ELF loader.

Synchronize FDPIC ELF aux vector setup with ELF. Replace entry-by-entry
aux vector copying to userspace with initialization of mm->saved_auxv
first and then copying it to userspace as a whole.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Link: https://lore.kernel.org/r/20240322195418.2160164-1-jcmvbkbc@gmail.com
Signed-off-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Max Filippov 2024-03-22 12:54:18 -07:00 committed by Kees Cook
parent 2a5eb99955
commit 10e29251be
1 changed files with 40 additions and 47 deletions
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87
fs/binfmt_elf_fdpic.c
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@ -505,8 +505,9 @@ static int create_elf_fdpic_tables(struct linux_binprm *bprm,
char *k_platform, *k_base_platform;
char __user *u_platform, *u_base_platform, *p;
int loop;
int nr; /* reset for each csp adjustment */
unsigned long flags = 0;
int ei_index;
elf_addr_t *elf_info;
#ifdef CONFIG_MMU
/* In some cases (e.g. Hyper-Threading), we want to avoid L1 evictions
@ -601,44 +602,24 @@ static int create_elf_fdpic_tables(struct linux_binprm *bprm,
csp -= sp & 15UL;
sp -= sp & 15UL;
/* put the ELF interpreter info on the stack */
#define NEW_AUX_ENT(id, val) \
do { \
struct { unsigned long _id, _val; } __user *ent, v; \
\
ent = (void __user *) csp; \
v._id = (id); \
v._val = (val); \
if (copy_to_user(ent + nr, &v, sizeof(v))) \
return -EFAULT; \
nr++; \
/* Create the ELF interpreter info */
elf_info = (elf_addr_t *)mm->saved_auxv;
/* update AT_VECTOR_SIZE_BASE if the number of NEW_AUX_ENT() changes */
#define NEW_AUX_ENT(id, val) \
do { \
*elf_info++ = id; \
*elf_info++ = val; \
} while (0)
nr = 0;
csp -= 2 * sizeof(unsigned long);
NEW_AUX_ENT(AT_NULL, 0);
if (k_platform) {
nr = 0;
csp -= 2 * sizeof(unsigned long);
NEW_AUX_ENT(AT_PLATFORM,
(elf_addr_t) (unsigned long) u_platform);
}
if (k_base_platform) {
nr = 0;
csp -= 2 * sizeof(unsigned long);
NEW_AUX_ENT(AT_BASE_PLATFORM,
(elf_addr_t) (unsigned long) u_base_platform);
}
if (bprm->have_execfd) {
nr = 0;
csp -= 2 * sizeof(unsigned long);
NEW_AUX_ENT(AT_EXECFD, bprm->execfd);
}
nr = 0;
csp -= DLINFO_ITEMS * 2 * sizeof(unsigned long);
#ifdef ARCH_DLINFO
/*
* ARCH_DLINFO must come first so PPC can do its special alignment of
* AUXV.
* update AT_VECTOR_SIZE_ARCH if the number of NEW_AUX_ENT() in
* ARCH_DLINFO changes
*/
ARCH_DLINFO;
#endif
NEW_AUX_ENT(AT_HWCAP, ELF_HWCAP);
#ifdef ELF_HWCAP2
NEW_AUX_ENT(AT_HWCAP2, ELF_HWCAP2);
@ -659,17 +640,29 @@ static int create_elf_fdpic_tables(struct linux_binprm *bprm,
NEW_AUX_ENT(AT_EGID, (elf_addr_t) from_kgid_munged(cred->user_ns, cred->egid));
NEW_AUX_ENT(AT_SECURE, bprm->secureexec);
NEW_AUX_ENT(AT_EXECFN, bprm->exec);
#ifdef ARCH_DLINFO
nr = 0;
csp -= AT_VECTOR_SIZE_ARCH * 2 * sizeof(unsigned long);
/* ARCH_DLINFO must come last so platform specific code can enforce
* special alignment requirements on the AUXV if necessary (eg. PPC).
*/
ARCH_DLINFO;
#endif
if (k_platform)
NEW_AUX_ENT(AT_PLATFORM,
(elf_addr_t)(unsigned long)u_platform);
if (k_base_platform)
NEW_AUX_ENT(AT_BASE_PLATFORM,
(elf_addr_t)(unsigned long)u_base_platform);
if (bprm->have_execfd)
NEW_AUX_ENT(AT_EXECFD, bprm->execfd);
#undef NEW_AUX_ENT
/* AT_NULL is zero; clear the rest too */
memset(elf_info, 0, (char *)mm->saved_auxv +
sizeof(mm->saved_auxv) - (char *)elf_info);
/* And advance past the AT_NULL entry. */
elf_info += 2;
ei_index = elf_info - (elf_addr_t *)mm->saved_auxv;
csp -= ei_index * sizeof(elf_addr_t);
/* Put the elf_info on the stack in the right place. */
if (copy_to_user((void __user *)csp, mm->saved_auxv,
ei_index * sizeof(elf_addr_t)))
return -EFAULT;
/* allocate room for argv[] and envv[] */
csp -= (bprm->envc + 1) * sizeof(elf_caddr_t);