| Message ID | 20220524055042.1527968-1-vaibhav@linux.ibm.com |
|---|---|
| State | Accepted |
| Commit | cbf9c4b9617b6767886a913705ca14b7600c77db |
| Headers | show |
| Series | [v2] of: check previous kernel's ima-kexec-buffer against memory bounds | expand |
Hi Ritesh, thanks for looking into this patch, Ritesh Harjani <ritesh.list@gmail.com> writes: > Just a minor nit which I noticed. > > On 22/05/24 11:20AM, Vaibhav Jain wrote: >> Presently ima_get_kexec_buffer() doesn't check if the previous kernel's >> ima-kexec-buffer lies outside the addressable memory range. This can result >> in a kernel panic if the new kernel is booted with 'mem=X' arg and the >> ima-kexec-buffer was allocated beyond that range by the previous kernel. >> The panic is usually of the form below: >> >> $ sudo kexec --initrd initrd vmlinux --append='mem=16G' >> >> <snip> >> BUG: Unable to handle kernel data access on read at 0xc000c01fff7f0000 >> Faulting instruction address: 0xc000000000837974 >> Oops: Kernel access of bad area, sig: 11 [#1] >> <snip> >> NIP [c000000000837974] ima_restore_measurement_list+0x94/0x6c0 >> LR [c00000000083b55c] ima_load_kexec_buffer+0xac/0x160 >> Call Trace: >> [c00000000371fa80] [c00000000083b55c] ima_load_kexec_buffer+0xac/0x160 >> [c00000000371fb00] [c0000000020512c4] ima_init+0x80/0x108 >> [c00000000371fb70] [c0000000020514dc] init_ima+0x4c/0x120 >> [c00000000371fbf0] [c000000000012240] do_one_initcall+0x60/0x2c0 >> [c00000000371fcc0] [c000000002004ad0] kernel_init_freeable+0x344/0x3ec >> [c00000000371fda0] [c0000000000128a4] kernel_init+0x34/0x1b0 >> [c00000000371fe10] [c00000000000ce64] ret_from_kernel_thread+0x5c/0x64 >> Instruction dump: >> f92100b8 f92100c0 90e10090 910100a0 4182050c 282a0017 3bc00000 40810330 >> 7c0802a6 fb610198 7c9b2378 f80101d0 <a1240000> 2c090001 40820614 e9240010 >> ---[ end trace 0000000000000000 ]--- >> >> Fix this issue by checking returned PFN range of previous kernel's >> ima-kexec-buffer with pfn_valid to ensure correct memory bounds. >> >> Fixes: 467d27824920 ("powerpc: ima: get the kexec buffer passed by the previous kernel") >> Cc: Frank Rowand <frowand.list@gmail.com> >> Cc: Prakhar Srivastava <prsriva@linux.microsoft.com> >> Cc: Lakshmi Ramasubramanian <nramas@linux.microsoft.com> >> Cc: Thiago Jung Bauermann <bauerman@linux.ibm.com> >> Cc: Rob Herring <robh@kernel.org> >> Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com> >> >> --- >> Changelog >> ========== >> >> v2: >> * Instead of using memblock to determine the valid bounds use pfn_valid() to do >> so since memblock may not be available late after the kernel init. [ Mpe ] >> * Changed the patch prefix from 'powerpc' to 'of' [ Mpe ] >> * Updated the 'Fixes' tag to point to correct commit that introduced this >> function. [ Rob ] >> * Fixed some whitespace/tab issues in the patch description [ Rob ] >> * Added another check for checking ig 'tmp_size' for ima-kexec-buffer is > 0 >> --- >> drivers/of/kexec.c | 17 +++++++++++++++++ >> 1 file changed, 17 insertions(+) >> >> diff --git a/drivers/of/kexec.c b/drivers/of/kexec.c >> index 8d374cc552be..879e984fe901 100644 >> --- a/drivers/of/kexec.c >> +++ b/drivers/of/kexec.c >> @@ -126,6 +126,7 @@ int ima_get_kexec_buffer(void **addr, size_t *size) >> { >> int ret, len; >> unsigned long tmp_addr; >> + unsigned int start_pfn, end_pfn; > > ^^^ Shouldn't this be unsigned long? Thanks for catching this. Yes that should be 'unsigned long'. Will resend the patch with this fixed. > > -ritesh > >> size_t tmp_size; >> const void *prop; >> >> @@ -140,6 +141,22 @@ int ima_get_kexec_buffer(void **addr, size_t *size) >> if (ret) >> return ret; >> >> + /* Do some sanity on the returned size for the ima-kexec buffer */ >> + if (!tmp_size) >> + return -ENOENT; >> + >> + /* >> + * Calculate the PFNs for the buffer and ensure >> + * they are with in addressable memory. >> + */ >> + start_pfn = PHYS_PFN(tmp_addr); >> + end_pfn = PHYS_PFN(tmp_addr + tmp_size - 1); >> + if (!pfn_valid(start_pfn) || !pfn_valid(end_pfn)) { >> + pr_warn("IMA buffer at 0x%lx, size = 0x%zx beyond memory\n", >> + tmp_addr, tmp_size); >> + return -EINVAL; >> + } >> + >> *addr = __va(tmp_addr); >> *size = tmp_size; >> >> -- >> 2.35.1 >>
diff --git a/drivers/of/kexec.c b/drivers/of/kexec.c index 8d374cc552be..879e984fe901 100644 --- a/drivers/of/kexec.c +++ b/drivers/of/kexec.c @@ -126,6 +126,7 @@ int ima_get_kexec_buffer(void **addr, size_t *size) { int ret, len; unsigned long tmp_addr; + unsigned int start_pfn, end_pfn; size_t tmp_size; const void *prop; @@ -140,6 +141,22 @@ int ima_get_kexec_buffer(void **addr, size_t *size) if (ret) return ret; + /* Do some sanity on the returned size for the ima-kexec buffer */ + if (!tmp_size) + return -ENOENT; + + /* + * Calculate the PFNs for the buffer and ensure + * they are with in addressable memory. + */ + start_pfn = PHYS_PFN(tmp_addr); + end_pfn = PHYS_PFN(tmp_addr + tmp_size - 1); + if (!pfn_valid(start_pfn) || !pfn_valid(end_pfn)) { + pr_warn("IMA buffer at 0x%lx, size = 0x%zx beyond memory\n", + tmp_addr, tmp_size); + return -EINVAL; + } + *addr = __va(tmp_addr); *size = tmp_size;
Presently ima_get_kexec_buffer() doesn't check if the previous kernel's ima-kexec-buffer lies outside the addressable memory range. This can result in a kernel panic if the new kernel is booted with 'mem=X' arg and the ima-kexec-buffer was allocated beyond that range by the previous kernel. The panic is usually of the form below: $ sudo kexec --initrd initrd vmlinux --append='mem=16G' <snip> BUG: Unable to handle kernel data access on read at 0xc000c01fff7f0000 Faulting instruction address: 0xc000000000837974 Oops: Kernel access of bad area, sig: 11 [#1] <snip> NIP [c000000000837974] ima_restore_measurement_list+0x94/0x6c0 LR [c00000000083b55c] ima_load_kexec_buffer+0xac/0x160 Call Trace: [c00000000371fa80] [c00000000083b55c] ima_load_kexec_buffer+0xac/0x160 [c00000000371fb00] [c0000000020512c4] ima_init+0x80/0x108 [c00000000371fb70] [c0000000020514dc] init_ima+0x4c/0x120 [c00000000371fbf0] [c000000000012240] do_one_initcall+0x60/0x2c0 [c00000000371fcc0] [c000000002004ad0] kernel_init_freeable+0x344/0x3ec [c00000000371fda0] [c0000000000128a4] kernel_init+0x34/0x1b0 [c00000000371fe10] [c00000000000ce64] ret_from_kernel_thread+0x5c/0x64 Instruction dump: f92100b8 f92100c0 90e10090 910100a0 4182050c 282a0017 3bc00000 40810330 7c0802a6 fb610198 7c9b2378 f80101d0 <a1240000> 2c090001 40820614 e9240010 ---[ end trace 0000000000000000 ]--- Fix this issue by checking returned PFN range of previous kernel's ima-kexec-buffer with pfn_valid to ensure correct memory bounds. Fixes: 467d27824920 ("powerpc: ima: get the kexec buffer passed by the previous kernel") Cc: Frank Rowand <frowand.list@gmail.com> Cc: Prakhar Srivastava <prsriva@linux.microsoft.com> Cc: Lakshmi Ramasubramanian <nramas@linux.microsoft.com> Cc: Thiago Jung Bauermann <bauerman@linux.ibm.com> Cc: Rob Herring <robh@kernel.org> Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com> --- Changelog ========== v2: * Instead of using memblock to determine the valid bounds use pfn_valid() to do so since memblock may not be available late after the kernel init. [ Mpe ] * Changed the patch prefix from 'powerpc' to 'of' [ Mpe ] * Updated the 'Fixes' tag to point to correct commit that introduced this function. [ Rob ] * Fixed some whitespace/tab issues in the patch description [ Rob ] * Added another check for checking ig 'tmp_size' for ima-kexec-buffer is > 0 --- drivers/of/kexec.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+)