On Thu, Apr 18, 2024 at 12:29:43PM +0200, Nam Cao wrote: > There is nothing preventing kernel memory allocators from allocating a > page that overlaps with PTR_ERR(), except for architecture-specific > code that setup memblock. > > It was discovered that RISCV architecture doesn't setup memblock > corectly, leading to a page overlapping with PTR_ERR() being allocated, > and subsequently crashing the kernel (link in Close: ) > > The reported crash has nothing to do with PTR_ERR(): the last page > (at address 0xfffff000) being allocated leads to an unexpected > arithmetic overflow in ext4; but still, this page shouldn't be > allocated in the first place. > > Because PTR_ERR() is an architecture-independent thing, we shouldn't > ask every single architecture to set this up. There may be other > architectures beside RISCV that have the same problem. > > Fix this one and for all by reserving the physical memory page that > may be mapped to the last virtual memory page as part of low memory. > > Unfortunately, this means if there is actual memory at this reserved > location, that memory will become inaccessible. However, if this page > is not reserved, it can only be accessed as high memory, so this > doesn't matter if high memory is not supported. Even if high memory is > supported, it is still only one page. > > Closes: https://lore.kernel.org/linux-riscv/878r1ibpdn.fsf@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx > Signed-off-by: Nam Cao <namcao@xxxxxxxxxxxxx> > Cc: <stable@xxxxxxxxxxxxxxx> # all versions > --- > init/main.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/init/main.c b/init/main.c > index 881f6230ee59..f8d2793c4641 100644 > --- a/init/main.c > +++ b/init/main.c > @@ -900,6 +900,7 @@ void start_kernel(void) > page_address_init(); > pr_notice("%s", linux_banner); > early_security_init(); > + memblock_reserve(__pa(-PAGE_SIZE), PAGE_SIZE); /* reserve last page for ERR_PTR */ > setup_arch(&command_line); > setup_boot_config(); > setup_command_line(command_line); > -- > 2.39.2 > I received a similar(ish) report recently https://lore.kernel.org/oe-kbuild-all/202404211031.J6l2AfJk-lkp@xxxxxxxxx/ regarding RISC-V in init/mail.c. Here is the meat of the report in case you want to avoid going to the actual link: " ... riscv64-linux-ld: section .data LMA [000000000099b000,0000000001424de7] overlaps section .text LMA [0000000000104040,000000000213c543] riscv64-linux-ld: section .data..percpu LMA [00000000024e2000,00000000026b46e7] overlaps section .rodata LMA [000000000213c580,000000000292d0dd] riscv64-linux-ld: section .rodata VMA [ffffffff8213c580,ffffffff8292d0dd] overlaps section .data VMA [ffffffff82000000,ffffffff82a89de7] init/main.o: in function `rdinit_setup': >> init/main.c:613:(.init.text+0x358): relocation truncated to fit: R_RISCV_GPREL_I against symbol `__setup_start' defined in .init.rodata section in .tmp_vmlinux.kallsyms1 net/ipv4/ipconfig.o: in function `ic_dhcp_init_options': net/ipv4/ipconfig.c:682:(.init.text+0x9b4): relocation truncated to fit: R_RISCV_GPREL_I against `ic_bootp_cookie' net/sunrpc/auth_gss/gss_krb5_mech.o: in function `gss_krb5_prepare_enctype_priority_list': >> net/sunrpc/auth_gss/gss_krb5_mech.c:213:(.text.gss_krb5_prepare_enctype_priority_list+0x9c): relocation truncated to fit: R_RISCV_GPREL_I against `gss_krb5_enctypes.0' lib/maple_tree.o: in function `mas_leaf_max_gap': >> lib/maple_tree.c:1512:(.text.mas_leaf_max_gap+0x2b8): relocation truncated to fit: R_RISCV_GPREL_I against `mt_pivots' lib/maple_tree.o: in function `ma_dead_node': >> lib/maple_tree.c:560:(.text.mas_data_end+0x110): relocation truncated to fit: R_RISCV_GPREL_I against `mt_pivots' lib/maple_tree.o: in function `mas_extend_spanning_null': >> lib/maple_tree.c:3662:(.text.mas_extend_spanning_null+0x69c): relocation truncated to fit: R_RISCV_GPREL_I against `mt_pivots' lib/maple_tree.o: in function `mas_mab_cp': >> lib/maple_tree.c:1943:(.text.mas_mab_cp+0x248): relocation truncated to fit: R_RISCV_GPREL_I against `mt_pivots' lib/maple_tree.o: in function `mab_mas_cp': >> lib/maple_tree.c:2000:(.text.mab_mas_cp+0x15c): relocation truncated to fit: R_RISCV_GPREL_I against `mt_pivots' lib/maple_tree.o: in function `mas_reuse_node': >> lib/maple_tree.c:3416:(.text.mas_reuse_node+0x17c): relocation truncated to fit: R_RISCV_GPREL_I against `mt_slots' lib/maple_tree.o: in function `mt_free_walk': >> lib/maple_tree.c:5238:(.text.mt_free_walk+0x15c): relocation truncated to fit: R_RISCV_GPREL_I against `mt_slots' lib/maple_tree.o: in function `mtree_lookup_walk': lib/maple_tree.c:3700:(.text.mtree_lookup_walk+0x94): additional relocation overflows omitted from the output ... " Could the fix that you have posted here be related to that report? Comments are greatly appreciated. Best -- Joel Granados
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