>From memfd_secret(2) manpage: The memory areas backing the file created with memfd_secret(2) are visible only to the processes that have access to the file descriptor. The memory region is removed from the kernel page tables and only the page tables of the processes holding the file descriptor map the corresponding physical memory. (Thus, the pages in the region can't be accessed by the kernel itself, so that, for example, pointers to the region can't be passed to system calls.) We need to handle this special case gracefully in build ID fetching code. Return -EFAULT whenever secretmem file is passed to build_id_parse() family of APIs. Original report and repro can be found in [0]. [0] https://lore.kernel.org/bpf/ZwyG8Uro%2FSyTXAni@ly-workstation/
Unified · Split
| @@ -5,6 +5,7 @@ · 4 unmodified lines | ||
| 5 | 5 | #include <linux/elf.h> |
| 6 | 6 | #include <linux/kernel.h> |
| 7 | 7 | #include <linux/pagemap.h> |
| 8 | +#include <linux/secretmem.h> | |
| 8 | 9 | |
| 9 | 10 | #define BUILD_ID 3 |
| 10 | 11 | |
| @@ -64,6 +65,10 @@ static int freader_get_folio(struct freader *r, loff_t file_off) · 53 unmodified lines | ||
| 64 | 65 | |
| 65 | 66 | freader_put_folio(r); |
| 66 | 67 | |
| 68 | + /* reject secretmem folios created with memfd_secret() */ | |
| 69 | + if (secretmem_mapping(r->file->f_mapping)) | |
| 70 | + return -EFAULT; | |
| 71 | + | |
| 67 | 72 | r->folio = filemap_get_folio(r->file->f_mapping, file_off >> PAGE_SHIFT); |
| 68 | 73 | |
| 69 | 74 | /* if sleeping is allowed, wait for the page, if necessary */ |