| Message ID | 20240322110058.557329-1-kazuma-kondo@nec.com |
|---|---|
| State | Accepted |
| Commit | 3cb4a4827596abc82e55b80364f509d0fefc3051 |
| Headers | show |
| Series | efi/libstub: fix efi_random_alloc() to allocate memory at alloc_min or higher address | expand |
Hello Ard Biesheuvel, On Fri, 22 Mar 2024 at 22:17, Ard Biesheuvel wrote: > On Fri, 22 Mar 2024 at 12:01, KONDO KAZUMA(近藤 和真) <kazuma-kondo@nec.com> wrote: >> >> Following warning is sometimes observed while booting my servers: >> [ 3.594838] DMA: preallocated 4096 KiB GFP_KERNEL pool for atomic allocations >> [ 3.602918] swapper/0: page allocation failure: order:10, mode:0xcc1(GFP_KERNEL|GFP_DMA), nodemask=(null),cpuset=/,mems_allowed=0-1 >> ... >> [ 3.851862] DMA: preallocated 1024 KiB GFP_KERNEL|GFP_DMA pool for atomic allocation >> >> If 'nokaslr' boot option is set, the warning always happens. >> >> On x86, ZONE_DMA is small zone at the first 16MB of physical address >> space. When this problem happens, most of that space seems to be used >> by decompressed kernel. Thereby, there is not enough space at DMA_ZONE >> to meet the request of DMA pool allocation. >> >> The commit 2f77465b05b1 ("x86/efistub: Avoid placing the kernel below LOAD_PHYSICAL_ADDR") >> tried to fix this problem by introducing lower bound of allocation. >> >> But the fix is not complete. >> >> efi_random_alloc() allocates pages by following steps. >> 1. Count total available slots ('total_slots') >> 2. Select a slot ('target_slot') to allocate randomly >> 3. Calculate a starting address ('target') to be included target_slot >> 4. Allocate pages, which starting address is 'target' >> >> In step 1, 'alloc_min' is used to offset the starting address of >> memory chunk. But in step 3 'alloc_min' is not considered at all. >> As the result, 'target' can be miscalculated and become lower >> than 'alloc_min'. >> >> When KASLR is disabled, 'target_slot' is always 0 and >> the problem happens everytime if the EFI memory map of the system >> meets the condition. >> >> Fix this problem by calculating 'target' considering 'alloc_min'. >> >> Cc: linux-efi@vger.kernel.org >> Cc: Tom Englund <tomenglund26@gmail.com> >> Cc: linux-kernel@vger.kernel.org >> Fixes: 2f77465b05b1 ("x86/efistub: Avoid placing the kernel below LOAD_PHYSICAL_ADDR") >> Signed-off-by: Kazuma Kondo <kazuma-kondo@nec.com> > > Hello Kazuma Kondo, > > Thanks for your patch. I will take it as a fix. > > You sent the same patch twice, right? Is there any difference between the two? Sorry for the confusion. I accidentally send same patch twice. So, please ignore the other patch which was sent by me on Fri, 22 Mar 2024 at 10:47 UTC. Thanks, Kazuma Kondo >> --- >> drivers/firmware/efi/libstub/randomalloc.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/drivers/firmware/efi/libstub/randomalloc.c b/drivers/firmware/efi/libstub/randomalloc.c >> index 4e96a855fdf4..7e1852859550 100644 >> --- a/drivers/firmware/efi/libstub/randomalloc.c >> +++ b/drivers/firmware/efi/libstub/randomalloc.c >> @@ -120,7 +120,7 @@ efi_status_t efi_random_alloc(unsigned long size, >> continue; >> } >> >> - target = round_up(md->phys_addr, align) + target_slot * align; >> + target = round_up(max(md->phys_addr, alloc_min), align) + target_slot * align; >> pages = size / EFI_PAGE_SIZE; >> >> status = efi_bs_call(allocate_pages, EFI_ALLOCATE_ADDRESS, >> -- >> 2.39.3
diff --git a/drivers/firmware/efi/libstub/randomalloc.c b/drivers/firmware/efi/libstub/randomalloc.c index 4e96a855fdf4..7e1852859550 100644 --- a/drivers/firmware/efi/libstub/randomalloc.c +++ b/drivers/firmware/efi/libstub/randomalloc.c @@ -120,7 +120,7 @@ efi_status_t efi_random_alloc(unsigned long size, continue; } - target = round_up(md->phys_addr, align) + target_slot * align; + target = round_up(max(md->phys_addr, alloc_min), align) + target_slot * align; pages = size / EFI_PAGE_SIZE; status = efi_bs_call(allocate_pages, EFI_ALLOCATE_ADDRESS,
Following warning is sometimes observed while booting my servers: [ 3.594838] DMA: preallocated 4096 KiB GFP_KERNEL pool for atomic allocations [ 3.602918] swapper/0: page allocation failure: order:10, mode:0xcc1(GFP_KERNEL|GFP_DMA), nodemask=(null),cpuset=/,mems_allowed=0-1 ... [ 3.851862] DMA: preallocated 1024 KiB GFP_KERNEL|GFP_DMA pool for atomic allocation If 'nokaslr' boot option is set, the warning always happens. On x86, ZONE_DMA is small zone at the first 16MB of physical address space. When this problem happens, most of that space seems to be used by decompressed kernel. Thereby, there is not enough space at DMA_ZONE to meet the request of DMA pool allocation. The commit 2f77465b05b1 ("x86/efistub: Avoid placing the kernel below LOAD_PHYSICAL_ADDR") tried to fix this problem by introducing lower bound of allocation. But the fix is not complete. efi_random_alloc() allocates pages by following steps. 1. Count total available slots ('total_slots') 2. Select a slot ('target_slot') to allocate randomly 3. Calculate a starting address ('target') to be included target_slot 4. Allocate pages, which starting address is 'target' In step 1, 'alloc_min' is used to offset the starting address of memory chunk. But in step 3 'alloc_min' is not considered at all. As the result, 'target' can be miscalculated and become lower than 'alloc_min'. When KASLR is disabled, 'target_slot' is always 0 and the problem happens everytime if the EFI memory map of the system meets the condition. Fix this problem by calculating 'target' considering 'alloc_min'. Cc: linux-efi@vger.kernel.org Cc: Tom Englund <tomenglund26@gmail.com> Cc: linux-kernel@vger.kernel.org Fixes: 2f77465b05b1 ("x86/efistub: Avoid placing the kernel below LOAD_PHYSICAL_ADDR") Signed-off-by: Kazuma Kondo <kazuma-kondo@nec.com> --- drivers/firmware/efi/libstub/randomalloc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)