On Mon, Apr 29, 2024 at 02:52:30PM +0200, Joel Granados wrote: > 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: This issue doesn't look like it has anything to do with this patch: this patch is about overlapping of dynamically allocated memory, while I think the issue is about overlapping sections during linking (maybe something wrong with riscv linker script?) Also, FWIW, this patch is not going to be in mainline because of a regression. Nonetheless, I will have a look at this later. Best regards, Nam > " > ... > 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
