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Thu, 26 Sep 2024 03:21:44 -0700 (PDT) From: Roger Pau Monne To: xen-devel@lists.xenproject.org Cc: Roger Pau Monne , Ross Lagerwall , Stefano Stabellini , Julien Grall , Bertrand Marquis , Michal Orzel , Volodymyr Babchuk , Jan Beulich , Andrew Cooper Subject: [PATCH v3 1/5] xen/livepatch: drop load_addr Elf section field Date: Thu, 26 Sep 2024 12:14:27 +0200 Message-ID: <20240926101431.97444-2-roger.pau@citrix.com> X-Mailer: git-send-email 2.46.0 In-Reply-To: <20240926101431.97444-1-roger.pau@citrix.com> References: <20240926101431.97444-1-roger.pau@citrix.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-ZohoMail-DKIM: pass (identity @citrix.com) X-ZM-MESSAGEID: 1727346129711116600 The Elf loading logic will initially use the `data` section field to stash a pointer to the temporary loaded data (from the buffer allocated in livepatch_upload(), which is later relocated and the new pointer stashed in `load_addr`. Remove this dual field usage and use an `addr` uniformly. Initially data w= ill point to the temporary buffer, until relocation happens, at which point the pointer will be updated to the relocated address. This avoids leaking a dangling pointer in the `data` field once the tempora= ry buffer is freed by livepatch_upload(). Note the `addr` field cannot retain the const attribute from the previous `data`field, as there's logic that performs manipulations against the loaded sections, like applying relocations or sorting the exception table. No functional change intended. Signed-off-by: Roger Pau Monn=C3=A9 Acked-by: Michal Orzel Reviewed-by: Andrew Cooper Reviewed-by: Ross Lagerwall --- Changes since v2: - New in this version. --- xen/arch/arm/arm32/livepatch.c | 8 +++--- xen/arch/arm/arm64/livepatch.c | 4 +-- xen/arch/x86/livepatch.c | 4 +-- xen/common/livepatch.c | 43 ++++++++++++++++++--------------- xen/common/livepatch_elf.c | 20 +++++++-------- xen/include/xen/livepatch_elf.h | 11 +++++---- 6 files changed, 47 insertions(+), 43 deletions(-) diff --git a/xen/arch/arm/arm32/livepatch.c b/xen/arch/arm/arm32/livepatch.c index d50066564666..134d07a175bb 100644 --- a/xen/arch/arm/arm32/livepatch.c +++ b/xen/arch/arm/arm32/livepatch.c @@ -239,20 +239,20 @@ int arch_livepatch_perform(struct livepatch_elf *elf, =20 if ( use_rela ) { - const Elf_RelA *r_a =3D rela->data + i * rela->sec->sh_entsize; + const Elf_RelA *r_a =3D rela->addr + i * rela->sec->sh_entsize; =20 symndx =3D ELF32_R_SYM(r_a->r_info); type =3D ELF32_R_TYPE(r_a->r_info); - dest =3D base->load_addr + r_a->r_offset; /* P */ + dest =3D base->addr + r_a->r_offset; /* P */ addend =3D r_a->r_addend; } else { - const Elf_Rel *r =3D rela->data + i * rela->sec->sh_entsize; + const Elf_Rel *r =3D rela->addr + i * rela->sec->sh_entsize; =20 symndx =3D ELF32_R_SYM(r->r_info); type =3D ELF32_R_TYPE(r->r_info); - dest =3D base->load_addr + r->r_offset; /* P */ + dest =3D base->addr + r->r_offset; /* P */ addend =3D get_addend(type, dest); } =20 diff --git a/xen/arch/arm/arm64/livepatch.c b/xen/arch/arm/arm64/livepatch.c index dfb72be44fb8..d80051f9dc67 100644 --- a/xen/arch/arm/arm64/livepatch.c +++ b/xen/arch/arm/arm64/livepatch.c @@ -246,9 +246,9 @@ int arch_livepatch_perform_rela(struct livepatch_elf *e= lf, =20 for ( i =3D 0; i < (rela->sec->sh_size / rela->sec->sh_entsize); i++ ) { - const Elf_RelA *r =3D rela->data + i * rela->sec->sh_entsize; + const Elf_RelA *r =3D rela->addr + i * rela->sec->sh_entsize; unsigned int symndx =3D ELF64_R_SYM(r->r_info); - void *dest =3D base->load_addr + r->r_offset; /* P */ + void *dest =3D base->addr + r->r_offset; /* P */ bool overflow_check =3D true; int ovf =3D 0; uint64_t val; diff --git a/xen/arch/x86/livepatch.c b/xen/arch/x86/livepatch.c index 4f76127e1f77..be40f625d206 100644 --- a/xen/arch/x86/livepatch.c +++ b/xen/arch/x86/livepatch.c @@ -258,9 +258,9 @@ int arch_livepatch_perform_rela(struct livepatch_elf *e= lf, =20 for ( i =3D 0; i < (rela->sec->sh_size / rela->sec->sh_entsize); i++ ) { - const Elf_RelA *r =3D rela->data + i * rela->sec->sh_entsize; + const Elf_RelA *r =3D rela->addr + i * rela->sec->sh_entsize; unsigned int symndx =3D ELF64_R_SYM(r->r_info); - uint8_t *dest =3D base->load_addr + r->r_offset; + uint8_t *dest =3D base->addr + r->r_offset; uint64_t val; =20 if ( symndx =3D=3D STN_UNDEF ) diff --git a/xen/common/livepatch.c b/xen/common/livepatch.c index df41dcce970a..7e6bf58f4408 100644 --- a/xen/common/livepatch.c +++ b/xen/common/livepatch.c @@ -371,18 +371,21 @@ static int move_payload(struct payload *payload, stru= ct livepatch_elf *elf) =20 ASSERT(offset[i] !=3D UINT_MAX); =20 - elf->sec[i].load_addr =3D buf + offset[i]; + buf +=3D offset[i]; =20 /* Don't copy NOBITS - such as BSS. */ if ( elf->sec[i].sec->sh_type !=3D SHT_NOBITS ) { - memcpy(elf->sec[i].load_addr, elf->sec[i].data, + memcpy(buf, elf->sec[i].addr, elf->sec[i].sec->sh_size); dprintk(XENLOG_DEBUG, LIVEPATCH "%s: Loaded %s at %p\n", - elf->name, elf->sec[i].name, elf->sec[i].load_addr= ); + elf->name, elf->sec[i].name, buf); } else - memset(elf->sec[i].load_addr, 0, elf->sec[i].sec->sh_size); + memset(buf, 0, elf->sec[i].sec->sh_size); + + /* Replace the temporary buffer with the relocated one. */ + elf->sec[i].addr =3D buf; } } =20 @@ -616,7 +619,7 @@ static inline int livepatch_check_expectations(const st= ruct payload *payload) break; = \ if ( !section_ok(elf, __sec, sizeof(*hook)) || __sec->sec->sh_size != =3D sizeof(*hook) ) \ return -EINVAL; = \ - hook =3D __sec->load_addr; = \ + hook =3D __sec->addr; = \ } while (0) =20 /* @@ -630,7 +633,7 @@ static inline int livepatch_check_expectations(const st= ruct payload *payload) break; = \ if ( !section_ok(elf, __sec, sizeof(*hook)) ) = \ return -EINVAL; = \ - hook =3D __sec->load_addr; = \ + hook =3D __sec->addr; = \ nhooks =3D __sec->sec->sh_size / sizeof(*hook); = \ } while (0) =20 @@ -650,7 +653,7 @@ static int prepare_payload(struct payload *payload, if ( !section_ok(elf, sec, sizeof(*payload->funcs)) ) return -EINVAL; =20 - payload->funcs =3D funcs =3D sec->load_addr; + payload->funcs =3D funcs =3D sec->addr; payload->nfuncs =3D sec->sec->sh_size / sizeof(*payload->funcs); =20 payload->fstate =3D xzalloc_array(typeof(*payload->fstate), @@ -709,7 +712,7 @@ static int prepare_payload(struct payload *payload, { const struct payload *data; =20 - n =3D sec->load_addr; + n =3D sec->addr; =20 if ( sec->sec->sh_size <=3D sizeof(*n) ) return -EINVAL; @@ -739,7 +742,7 @@ static int prepare_payload(struct payload *payload, sec =3D livepatch_elf_sec_by_name(elf, ELF_LIVEPATCH_DEPENDS); if ( sec ) { - n =3D sec->load_addr; + n =3D sec->addr; =20 if ( sec->sec->sh_size <=3D sizeof(*n) ) return -EINVAL; @@ -755,7 +758,7 @@ static int prepare_payload(struct payload *payload, sec =3D livepatch_elf_sec_by_name(elf, ELF_LIVEPATCH_XEN_DEPENDS); if ( sec ) { - n =3D sec->load_addr; + n =3D sec->addr; =20 if ( sec->sec->sh_size <=3D sizeof(*n) ) return -EINVAL; @@ -794,8 +797,8 @@ static int prepare_payload(struct payload *payload, if ( !section_ok(elf, sec, sizeof(*region->frame[i].start)) ) return -EINVAL; =20 - region->frame[i].start =3D sec->load_addr; - region->frame[i].stop =3D sec->load_addr + sec->sec->sh_size; + region->frame[i].start =3D sec->addr; + region->frame[i].stop =3D sec->addr + sec->sec->sh_size; } =20 sec =3D livepatch_elf_sec_by_name(elf, ".altinstructions"); @@ -843,8 +846,8 @@ static int prepare_payload(struct payload *payload, return -EINVAL; } =20 - start =3D sec->load_addr; - end =3D sec->load_addr + sec->sec->sh_size; + start =3D sec->addr; + end =3D sec->addr + sec->sec->sh_size; =20 for ( a =3D start; a < end; a++ ) { @@ -867,14 +870,14 @@ static int prepare_payload(struct payload *payload, * repl must be fully within .altinstr_replacement, even if the * replacement and the section happen to both have zero length. */ - if ( repl < repl_sec->load_addr || + if ( repl < repl_sec->addr || a->repl_len > repl_sec->sec->sh_size || - repl + a->repl_len > repl_sec->load_addr + repl_sec->sec-= >sh_size ) + repl + a->repl_len > repl_sec->addr + repl_sec->sec->sh_s= ize ) { printk(XENLOG_ERR LIVEPATCH "%s Alternative repl %p+%#x outside .altinstr_repla= cement %p+%#"PRIxElfWord"\n", elf->name, repl, a->repl_len, - repl_sec->load_addr, repl_sec->sec->sh_size); + repl_sec->addr, repl_sec->sec->sh_size); return -EINVAL; } } @@ -896,8 +899,8 @@ static int prepare_payload(struct payload *payload, if ( !section_ok(elf, sec, sizeof(*region->ex)) ) return -EINVAL; =20 - s =3D sec->load_addr; - e =3D sec->load_addr + sec->sec->sh_size; + s =3D sec->addr; + e =3D sec->addr + sec->sec->sh_size; =20 sort_exception_table(s ,e); =20 @@ -916,7 +919,7 @@ static int prepare_payload(struct payload *payload, if ( !section_ok(elf, sec, sizeof(*payload->metadata.data)) ) return -EINVAL; =20 - payload->metadata.data =3D sec->load_addr; + payload->metadata.data =3D sec->addr; payload->metadata.len =3D sec->sec->sh_size; =20 /* The metadata is required to consists of null terminated strings= . */ diff --git a/xen/common/livepatch_elf.c b/xen/common/livepatch_elf.c index 45d73912a3cd..25ce1bd5a0ad 100644 --- a/xen/common/livepatch_elf.c +++ b/xen/common/livepatch_elf.c @@ -36,7 +36,7 @@ static int elf_verify_strtab(const struct livepatch_elf_s= ec *sec) if ( !s->sh_size ) return -EINVAL; =20 - contents =3D sec->data; + contents =3D sec->addr; =20 if ( contents[0] || contents[s->sh_size - 1] ) return -EINVAL; @@ -44,7 +44,7 @@ static int elf_verify_strtab(const struct livepatch_elf_s= ec *sec) return 0; } =20 -static int elf_resolve_sections(struct livepatch_elf *elf, const void *dat= a) +static int elf_resolve_sections(struct livepatch_elf *elf, void *data) { struct livepatch_elf_sec *sec; unsigned int i; @@ -104,7 +104,7 @@ static int elf_resolve_sections(struct livepatch_elf *e= lf, const void *data) sec[i].sec->sh_size > LIVEPATCH_MAX_SIZE ) return -EINVAL; =20 - sec[i].data =3D data + delta; + sec[i].addr =3D data + delta; /* Name is populated in elf_resolve_section_names. */ sec[i].name =3D NULL; =20 @@ -226,14 +226,14 @@ static int elf_get_sym(struct livepatch_elf *elf, con= st void *data) strtab_sec =3D elf->strtab; =20 /* Pointers arithmetic to get file offset. */ - offset =3D strtab_sec->data - data; + offset =3D strtab_sec->addr - data; =20 /* Checked already in elf_resolve_sections, but just in case. */ ASSERT(offset =3D=3D strtab_sec->sec->sh_offset); ASSERT(offset < elf->len && (offset + strtab_sec->sec->sh_size <=3D el= f->len)); =20 - /* symtab_sec->data was computed in elf_resolve_sections. */ - ASSERT((symtab_sec->sec->sh_offset + data) =3D=3D symtab_sec->data); + /* symtab_sec->addr was computed in elf_resolve_sections. */ + ASSERT((symtab_sec->sec->sh_offset + data) =3D=3D symtab_sec->addr); =20 /* No need to check values as elf_resolve_sections did it. */ nsym =3D symtab_sec->sec->sh_size / symtab_sec->sec->sh_entsize; @@ -251,7 +251,7 @@ static int elf_get_sym(struct livepatch_elf *elf, const= void *data) =20 for ( i =3D 1; i < nsym; i++ ) { - const Elf_Sym *s =3D symtab_sec->data + symtab_sec->sec->sh_entsiz= e * i; + const Elf_Sym *s =3D symtab_sec->addr + symtab_sec->sec->sh_entsiz= e * i; =20 delta =3D s->st_name; /* Boundary check within the .strtab. */ @@ -263,7 +263,7 @@ static int elf_get_sym(struct livepatch_elf *elf, const= void *data) } =20 sym[i].sym =3D s; - sym[i].name =3D strtab_sec->data + delta; + sym[i].name =3D strtab_sec->addr + delta; if ( arch_livepatch_symbol_deny(elf, &sym[i]) ) { printk(XENLOG_ERR LIVEPATCH "%s: Symbol '%s' should not be in = payload\n", @@ -342,7 +342,7 @@ int livepatch_elf_resolve_symbols(struct livepatch_elf = *elf) break; } =20 - st_value +=3D (unsigned long)elf->sec[idx].load_addr; + st_value +=3D (unsigned long)elf->sec[idx].addr; if ( elf->sym[i].name ) dprintk(XENLOG_DEBUG, LIVEPATCH "%s: Symbol resolved: %s = =3D> %#"PRIxElfAddr" (%s)\n", elf->name, elf->sym[i].name, @@ -503,7 +503,7 @@ static int livepatch_header_check(const struct livepatc= h_elf *elf) return 0; } =20 -int livepatch_elf_load(struct livepatch_elf *elf, const void *data) +int livepatch_elf_load(struct livepatch_elf *elf, void *data) { int rc; =20 diff --git a/xen/include/xen/livepatch_elf.h b/xen/include/xen/livepatch_el= f.h index 7116deaddc28..842111e14518 100644 --- a/xen/include/xen/livepatch_elf.h +++ b/xen/include/xen/livepatch_elf.h @@ -13,10 +13,11 @@ struct livepatch_elf_sec { const Elf_Shdr *sec; /* Hooked up in elf_resolve_secti= ons.*/ const char *name; /* Human readable name hooked in elf_resolve_section_names. */ - const void *data; /* Pointer to the section (done by - elf_resolve_sections). */ - void *load_addr; /* A pointer to the allocated des= tination. - Done by load_payload_data. */ + void *addr; /* + * Pointer to the section. This = is + * first a temporary buffer, then + * later the relocated load addre= ss. + */ }; =20 struct livepatch_elf_sym { @@ -41,7 +42,7 @@ struct livepatch_elf { const struct livepatch_elf_sec * livepatch_elf_sec_by_name(const struct livepatch_elf *elf, const char *name); -int livepatch_elf_load(struct livepatch_elf *elf, const void *data); +int livepatch_elf_load(struct livepatch_elf *elf, void *data); void livepatch_elf_free(struct livepatch_elf *elf); =20 int livepatch_elf_resolve_symbols(struct livepatch_elf *elf); --=20 2.46.0