Thank you for your contribution! Sashiko AI review found 3 potential issue(s) to consider: - [High] Calling printk (via dbg_sec and dbg_sec_ehfh) while user access (UACCESS) is enabled. - [High] Missing cond_resched() in massive, unbounded .eh_frame validation loop. - [High] Misuse of scoped_user_read_access_size completely bypasses pointer masking mitigations. --
--- Patch [14]: [RFC PATCH v2 14/24] unwind_user/eh_frame: Add .eh_frame[_hdr] validation option --- commit e134b713f5753b4c2aa710bb7ce4a784930e6ccd Author: Jens Remus <[email protected]> unwind_user/eh_frame: Add .eh_frame[_hdr] validation option Add a debug feature to validate all .eh_frame[_hdr] sections when first loading the file rather than on demand. > diff --git a/kernel/unwind/eh_frame.c b/kernel/unwind/eh_frame.c > index 96237a96d263e..b0be56e315080 100644 > --- a/kernel/unwind/eh_frame.c > +++ b/kernel/unwind/eh_frame.c [ ... ] > @@ -1216,6 +1216,92 @@ int eh_frame_find(unsigned long ip, struct > unwind_user_frame *frame) > return ret; > } > > +#ifdef CONFIG_EH_FRAME_VALIDATION > + > +static int eh_frame_validate_section(struct eh_frame_section *sec) > +{ [ ... ] > + table_start_ptr = (void __user *)sec->binary_search_table_start; > + table_size = sec->binary_search_table_end - > sec->binary_search_table_start; > + > + for (i = 0; i < sec->fde_count; i++) { [Severity: High] Could this unbounded loop cause CPU stalls or trigger soft lockup warnings? Since fde_count is controlled by the size of the mapped .eh_frame_hdr VMA, it can be extremely large for maliciously crafted ELF files, potentially stalling the CPU for seconds or minutes. Because mmap_read_lock is released before this is called, would it be safer to add a cond_resched() in this loop? > + struct eh_frame_fde fde; > + unsigned long cur; > + unsigned long func_addr, fde_addr; > + int ret; > + > + cur = sec->binary_search_table_start + i * entry_size; > + > + scoped_user_read_access_size(table_start_ptr, table_size, > Efault) { > + /* Read function start address from table */ > + ret = read_encoded_pointer(sec, &cur, > + sec->binary_search_table_end, > + table_enc, &func_addr); [Severity: High] Does this bypass the Spectre v1 mitigations provided by the scoped access macro? The scoped_user_read_access_size() macro shadows the table_start_ptr variable to enforce usage of a masked pointer. However, the code ignores that masked pointer and instead uses the unmasked cur pointer derived outside the scope: cur = sec->binary_search_table_start + i * entry_size; When read_encoded_pointer() uses this unmasked pointer inside unsafe_get_user(), the masking mitigations are bypassed, allowing potential arbitrary speculative reads. > + if (ret) { > + dbg_sec_ehfh(cur, "table[%lu]: failed to read > function start address\n", i); [Severity: High] Is it safe to call printk wrappers like dbg_sec_ehfh() or dbg_sec() while user access (UACCESS) is enabled? Calling complex functions like printk inside a scoped_user_read_access_size() block can lead to deadlocks or kernel panics. It does internal locking, can sleep, and may clobber architecture-specific user access state like the SMAP AC flag. > + return ret; > + } > + if (i && func_addr <= prev_func_addr) { > + dbg_sec(".eh_frame_hdr: table[%lu]: not > sorted\n", i); > + return -EINVAL; > + } -- Sashiko AI review ยท https://sashiko.dev/#/patchset/[email protected]?part=14
