linux-kernel - [PATCH v2 2/4] riscv: Correctly free relocation hashtable on error

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Message-Id: <20240103-module_loading_fix-v2-2-292b160552c9@rivosinc.com>
Date: Wed, 03 Jan 2024 12:22:01 -0800
From: Charlie Jenkins <charlie@...osinc.com>
To: Paul Walmsley <paul.walmsley@...ive.com>, 
 Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>
Cc: Palmer Dabbelt <palmer@...osinc.com>, linux-riscv@...ts.infradead.org, 
 linux-kernel@...r.kernel.org, Charlie Jenkins <charlie@...osinc.com>, 
 kernel test robot <lkp@...el.com>, Dan Carpenter <dan.carpenter@...aro.org>, 
 Julia Lawall <julia.lawall@...ia.fr>
Subject: [PATCH v2 2/4] riscv: Correctly free relocation hashtable on error

When there is not enough allocatable memory for the relocation
hashtable, module loading should exit gracefully. Previously, this was
attempted to be accomplished by checking if an unsigned number is less
than zero which does not work. Instead have the caller check if the
hashtable was correctly allocated and add a comment explaining that
hashtable_bits that is 0 is valid.

Signed-off-by: Charlie Jenkins <charlie@...osinc.com>
Fixes: d8792a5734b0 ("riscv: Safely remove entries from relocation list")
Reported-by: kernel test robot <lkp@...el.com>
Reported-by: Dan Carpenter <dan.carpenter@...aro.org>
Closes: https://lore.kernel.org/r/202312132019.iYGTwW0L-lkp@intel.com/
Reported-by: kernel test robot <lkp@...el.com>
Reported-by: Julia Lawall <julia.lawall@...ia.fr>
Closes: https://lore.kernel.org/r/202312120044.wTI1Uyaa-lkp@intel.com/
---
 arch/riscv/kernel/module.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/arch/riscv/kernel/module.c b/arch/riscv/kernel/module.c
index 21c7a773a8ef..32743180e8ef 100644
--- a/arch/riscv/kernel/module.c
+++ b/arch/riscv/kernel/module.c
@@ -747,6 +747,10 @@ initialize_relocation_hashtable(unsigned int num_relocations,
 {
 	/* Can safely assume that bits is not greater than sizeof(long) */
 	unsigned long hashtable_size = roundup_pow_of_two(num_relocations);
+	/*
+	 * When hashtable_size == 1, hashtable_bits == 0.
+	 * This is valid because the hashing algorithm returns 0 in this case.
+	 */
 	unsigned int hashtable_bits = ilog2(hashtable_size);
 
 	/*
@@ -763,7 +767,7 @@ initialize_relocation_hashtable(unsigned int num_relocations,
 					      sizeof(*relocation_hashtable),
 					      GFP_KERNEL);
 	if (!*relocation_hashtable)
-		return -ENOMEM;
+		return 0;
 
 	__hash_init(*relocation_hashtable, hashtable_size);
 
@@ -789,8 +793,8 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
 	hashtable_bits = initialize_relocation_hashtable(num_relocations,
 							 &relocation_hashtable);
 
-	if (hashtable_bits < 0)
-		return hashtable_bits;
+	if (!relocation_hashtable)
+		return -ENOMEM;
 
 	INIT_LIST_HEAD(&used_buckets_list);
 

-- 
2.43.0